Group: alt.sys.pdp8, Item 1167 Subject: 'Testing mail to news gateway' From: walstib@andronix.org ('What A Long Strange Trip It's Been'), Yale CS Mail/ Date: 5 Dec 1994 15:58:41 -0500 Testing mail to news gateway; please ignore... =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=* What_A_Long_Strange_Trip_It's_Been:_A_Hippy's_History_Of_The_60's_And_Beyond (C) 1989 and 1994 By Lewis Sanders ISBN 0-9643083-0-4 Autographed copies free of charge -- Dealer and Quantity Discounts Available Still Steaming Press, c/o 637 South Broadway B-317, Boulder, Colorado, 80303 =*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=* --> For excerpts, reviews, & details, email 'walstib-info@andronix.org'! <-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ From jones@pyrite.cs.uiowa.edu Fri Dec 9 17:54:23 EST 1994 Article: 1114 of alt.sys.pdp8 Path: bigblue.oit.unc.edu!concert!gatech!howland.reston.ans.net!pipex!uunet!news.uiowa.edu!news From: jones@pyrite.cs.uiowa.edu (Douglas W. Jones,201H MLH,3193350740,3193382879) Newsgroups: sci.electronics,alt.sys.pdp8 Subject: Re: Need Orbis Floppy for PDP8 Date: 8 Dec 1994 17:00:29 GMT Organization: University of Iowa, Iowa City, IA, USA Lines: 12 Distribution: world Message-ID: <3c7e3d$aul@nexus.uiowa.edu> References: <3c5k3b$31v@newsbf01.news.aol.com> NNTP-Posting-Host: pyrite.cs.uiowa.edu Xref: bigblue.oit.unc.edu sci.electronics:94900 alt.sys.pdp8:1114 From article <3c5k3b$31v@newsbf01.news.aol.com>, by mikes1855@aol.com (MikeS1855): > If anyone has an old Orbis Floppy with a PDP8-620 or PDP8E controller > interface or knows where I might be able to find one, please let me know > by e-mail. I am looking for one. Thank you, Mike The above note should have been posted to alt.sys.pdp8, the preferred newsgroup for discussion of PDP-8 systems. The group comp.sys.dec might also have been appropriate. Doug Jones jones@cs.uiowa.edu Article 1115 of alt.sys.pdp8: Path: bigblue.oit.unc.edu!concert!theo!news-server.ncren.net!taco.cc.ncsu.edu!gatech!swrinde!pipex!uunet!news.uiowa.edu!news From: jones@cs.uiowa.edu (Douglas W. Jones) Newsgroups: alt.sys.pdp8,alt.answers,news.answers Subject: PDP-8 Frequently Asked Questions (posted every other month) Followup-To: alt.sys.pdp8 Date: 8 Dec 1994 08:08:08 GMT Organization: Computer Science, University of Iowa, Iowa City, Iowa, USA Lines: 1160 Approved: news-answers-request@MIT.Edu Distribution: world Expires: 8 Feb 1995 08:08:08 GMT Message-ID: <3c7bli$9cm@nexus.uiowa.edu> NNTP-Posting-Host: pyrite.cs.uiowa.edu Summary: Answers to common questions about antique DEC PDP-8 computers. Those posting to alt.sys.pdp8 should read this. Keywords: FAQ DEC PDP 8 Xref: bigblue.oit.unc.edu alt.sys.pdp8:1115 alt.answers:5908 news.answers:32284 Archive-name: dec-faq/pdp8 Last-modified: Dec 8, 1994 Frequently Asked Questions about the DEC PDP-8 computer. By Douglas Jones, jones@cs.uiowa.edu (with help from many folks) The most recent version of this file is available by anonymous FTP from: ftp://rtfm.mit.edu/pub/usenet/alt.sys.pdp8 ftp://ftp.uu.net/usenet/news.answers/dec-faq ftp://src.doc.ic.ac.uk:/pub/usenet/news.answers/alt.sys.pdp8 ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/docs Automatic translations of this document to HTML format (as used by World Wide Web) are available from: http://www.cis.ohio-state.edu/hypertext/faq/usenet/dec-faq/top.html An obsolete version of this file is available on the Walnut Creek USENET FAQ CDROM. This posting conforms to RFC1153 USENET digest format (with exceptions due to the fact that it is not really a digest). Contents: What is a PDP? What is a PDP-8? What is the PDP-8 instruction set? What does PDP-8 assembly language look like? What character sets does the PDP-8 support? What different PDP-8 models were made? What about the LINC-8 and PDP-12? Where can I get a PDP-8 today? Where can I get PDP-8 documentation? What operating systems were written for the PDP-8? What programming languages were supported on the PDP-8? Where can I get PDP-8 software? Where can I get additional information? What use is a PDP-8 today? Who's Who? ---------------------------------------------------------------------- Subject: What is a PDP? In 1957, Ken Olson and Harlan Anderson founded Digital Equipment Corporation (DEC), capitalized at $100,000, and 70% owned by American Research and Development Corporation. The founders wanted to call the company Digital Computer Corporation, but the venture capitalists insisted that they avoid the term Computer and hold off on building computers. With facilities in an old woolen mill in Maynard Massachusetts, DEC's first product was a line of transistorized digital "systems modules", plug-in circuit boards with a few logic gates per board. Starting in 1960, DEC finally began to sell computers (the formal acceptance of the first PDP-1 by BBN is reported in Computers and Automation, April 1961, page 8B). Soon after this, there were enough users that DECUS, the Digital Equipment Computer User's Society was founded. DEC's first computer, the PDP-1, sold for only $120,000 at a time when other computers sold for over $1,000,000. (A good photo of a PDP-1 is printed in Computers and Automation, Dec. 1961, page 27). DEC quoted prices as low as $85,000 for minimal models. The venture capitalist's insistance on avoiding the term computer was based on the stereotype that computers were big and expensive, needing a computer center and a large staff; by using the term Programmable Data Processor, or PDP, DEC avoided this stereotype. For over a decade, all digital computers sold by DEC were called PDPs. (In early DEC documentation, the plural form "PDPs" is used as a generic term for all DEC computers.) In the early 1960's, DEC was the only manufacturer of large computers without a leasing plan. IBM, Burroughs, CDC and other computer manufacturers leased most of their machines, and many machines were never offered for outright sale. DEC's cash sales approach led to the growth of third party computer leasing companies such as DELOS, a spinoff of BB&N. DEC built a number of different computers under the PDP label, with a huge range of price and performance. The largest of these are fully worthy of large computer centers with big support staffs. Some early DEC computers were not really built by DEC. With the PDP-3 and LINC, for example, customers built the machines using DEC parts and facilities. Here is the list of PDP computers: MODEL DATE PRICE BITS COMMENTS ===== ==== ======== ==== ===== PDP-1 1960 $120,000 18 DEC's first computer PDP-2 NA 24 Never built? PDP-3 NA 36 One built by a customer, not by DEC. PDP-4 1962 $60,000 18 Predecessor of the PDP-7. PDP-5 1963 $27,000 12 The ancestor of the PDP-8. PDP-6 1964 $300,000 36 A big computer; 23 built, most for MIT. PDP-7 1965 $72,000 18 Widely used for real-time control. PDP-8 1965 $18,500 12 The smallest and least expensive PDP. PDP-9 1966 $35,000 18 An upgrade of the PDP-7. PDP-10 1967 $110,000 36 A PDP-6 followup, great for timesharing. PDP-11 1970 $10,800 16 DEC's first and only 16 bit computer. PDP-12 1969 $27,900 12 A PDP-8 relative. PDP-13 NA Bad luck, there was no such machine. PDP-14 A ROM-based programmable controller. PDP-15 1970 $16,500 18 A TTL upgrade of the PDP-9. PDP-16 1972 NA 8/16 A register-transfer module system. Corrections and additions to this list are welcome! The prices given are for minimal systems in the year the machine was first introduced. The bits column indicates the word size. Note that the DEC PDP-10 became the DECSYSTEM-20 as a result of marketing considerations, and DEC's VAX series of machines began as the Virtual Address eXtension of the never-produced PDP-11/78. It is worth mentioning that it is generally accepted that the Data General Nova (see photo, Computers and Automation, Nov. 1968, page 48) was originally developed as the PDP-X, a 16-bit multi-register version of the PDP-8. A prototype PDP-X was built at DEC before the design was rejected. This and a competing 16-bit design were apparently submitted to Harold McFarland at Carnegie-Mellon University for evaluation; McFarland (and perhaps Gordon Bell, who was at C-MU at the time) evaluated the competing designs and rejected both in favor of what we know as the PDP-11. Some speculate that Bell rejected the Nova design because the competing proposal used the register-transfer notation he had introduced in "Bell and Newell, Computer Structures -- Readings and Examples". An alternate story is that the reason DEC never produced a PDP-13 was because the number 13 had been assigned to what became the Nova; this is unlikely because the PDP-X prototype came before the -11. Neither DEC nor Data General talk much about this, but Ed De Castro, the founding president of Data General, was part of the PDP-8 design team, as were many of the others who came to Data General to build the Nova. Today, all of the PDP machines are in DEC's corporate past, with the exception of the PDP-11 family, which survives as a line of microcomputers. Of course, occasionally, some lab builds a machine out of DEC hardware and calls it a PDP with a new number. For example, the Australian Atomic Energy Commission once upgraded a PDP-7 by adding a PDP-15 on the side; they called the result a PDP-22. ------------------------------ Subject: What is a PDP-8? The PDP-8 family of minicomputers were built by Digital Equipment Corporation between 1965 and 1990, although it is worth noting that the term minicomputer first came into prominence after the machine was introduced. The first use of the term appears to have been made by the head of DEC's operations in England, John Leng. He sent back a sales report that started: "Here is the latest minicomputer activity in the land of miniskirts as I drive around in my [Austin] Mini Minor." The term quickly became part of DEC's internal jargon and spread from there; the first computer explicitly sold as a minicomputer, though, was made by by Interdata (See the Interdata ad in Computers and Automation, May 1968, page 10). The PDP-8 was largely upward compatible with the PDP-5, a machine that was unveiled on August 11, 1963 at WESCON, and the inspiration for that machine came from two earlier machines, the LINC and the CDC 160. All of these machines were characterized by a 12 bit word with little or no hardware byte structure, typically 4K words of memory, and simple but powerful instruction sets. Although some people consider the CDC 160 the first minicomputer, the PDP-8 was the definitive minicomputer. By late 1973, the PDP-8 family was the best selling computer in the world, and it is likely that it was only displaced from this honor by the Apple II (which was displaced by the IBM PC). Most models of the PDP-8 set new records as the least expensive computer on the market at the time of their introduction. The PDP-8 has been described as the model-T of the computer industry because it was the first computer to be mass produced at a cost that just about anyone could afford. C. Gordon Bell has said that the basic idea of the PDP-8 was not really original with him. He gives credit to Seymour Cray (of CDC and later Cray) for the idea of a single-accumulator 12 bit minicomputer. Cray's CDC 160 family (see CACM, march 1961, photo on page 244, text on page 246) was such a machine, and in addition to the hundreds of CDC 160 systems sold as stand-alone machines, a derivative 12 bit architecture was used for the I/O processors on Cray's first great supercomputer, the CDC 6600. Note that Cray's 12 bit machines had 6 basic addressing modes with variable length instruction words and other features that were far from the simple elegance of the PDP-8. Despite its many modes, the CDC architecture lacked the notion of current page addressing, and the result is that, for examples that don't involve indexing, PDP-8 code is generally as tight as and perhaps tighter than CDC 160 code. ------------------------------ Subject: What is the PDP-8 instruction set? The PDP-8 word size is 12 bits, and the basic memory is 4K words. The minimal CPU contained the following registers: PC - the program counter, 12 bits. AC - the accumulator, 12 bits. L - the link, 1 bit, commonly prefixed to AC as . It is worth noting that many operations such as procedure linkage and indexing, which are usually thought of as involving registers, are done with memory on the PDP-8 family. Instruction words are organized as follows: _ _ _ _ _ _ _ _ _ _ _ _ |_|_|_|_|_|_|_|_|_|_|_|_| | | | | | | op |i|z| addr | op - the opcode. i - the indirect bit (0 = direct, 1 = indirect). z - the page bit (0 = page zero, 1 = current page). addr - the word in page. The top 5 bits of the 12 bit program counter give the current page, and memory addressing is also complicated by the fact that absolute memory locations 8 through 15 are incremented prior to use when used as indirect addresses. These locations are called auto-index registers (despite the fact that they are in memory); they allow the formulation of very tightly coded array operations. The basic instructions are: 000 - AND - and operand with AC. 001 - TAD - add operand to (a 13 bit value). 010 - ISZ - increment operand and skip if result is zero. 011 - DCA - deposit AC in memory and clear AC. 100 - JMS - jump to subroutine. 101 - JMP - jump. 110 - IOT - input/output transfer. 111 - OPR - microcoded operations. The ISZ and other skip instructions conditionally skip the next instruction in sequence. The ISZ is commonly used to increment a loop counter and skip if done, and it is also used as an general increment instruction, either followed by a no-op or in contexts where it is known that the result will never be zero. The JMS instruction stores the return address in relative word zero of the subroutine, with execution starting with relative word one. Subroutine return is done with an indirect JMP through the return address. Subroutines commonly increment their return addresses to index through inline parameter lists or to perform conditional skips over instructions following the call. The IOT instruction has the following form: _ _ _ _ _ _ _ _ _ _ _ _ |1|1|0|_|_|_|_|_|_|_|_|_| | | | | | | device | op | The IOT instruction specifies one of up to 8 operations on one of 64 devices. Typically (but not universally), each bit of the op field evokes an operation, and these can be microcoded in right to left order. Prior to the PDP-8/E, there were severe restrictions on the interpretation of the op field that resulted from the fact that the operation was delivered as a sequence of IOP pulses, each on a separate line of the I/O bus. Each line was typically used to evoke a different device function, so essentially, the operation 000 was always a no-op because it evoked no functions, and the code 111 evoked all three functions in series. As an example of the use of IOT instructions, consider the console terminal interface. On early PDP-8 systems, this was always assumed to be an ASR 33 teletype, complete with low-speed paper tape reader and punch. It was addressed as devices 03 (the keyboard/reader) and 04 (the teleprinter/punch): _ _ _ _ _ _ _ _ _ _ _ _ |1|1|0|_|_|_|_|_|_|_|_|_| |0 0 0 0 1 1|0 0 1 - KSF - keyboard skip if flag |0 0 0 0 1 1|0 1 0 - KCC - keyboard clear flag |0 0 0 0 1 1|1 0 0 - KRS - keyboard read static The keyboard flag is set by the arrival of a character. The KCC instruction clears both the flag and the accumulator. KRS ors the 8 bit input data with the low order 8 bits of AC. The commonly used KRB instruction is the or of KCC and KRS. To await one byte of input, use KSF to poll the flag, then read the byte with KRB. _ _ _ _ _ _ _ _ _ _ _ _ |1|1|0|_|_|_|_|_|_|_|_|_| |0 0 0 1 0 0|0 0 1 - TSF - teleprinter skip if flag |0 0 0 1 0 0|0 1 0 - TCF - teleprinter clear flag |0 0 0 1 0 0|1 0 0 - TPC - teleprinter print static The teleprinter flag is set by the completion of the TPC operation (as a result, on startup, many applications output a null in order to get things going). TCF clears the flag, and TPC outputs the low order 8 bits of the accumulator. The commonly used TLS instruction is the or of TCF and TPC. To output a character, first use TSF to poll the flag, then write the character with TLS. IOT instructions may be used to initiate data break transfers from block devices such as disk or tape. The term "data break" was, for years, DEC's preferred term for cycle-stealing direct-memory-access data transfers. Some CPU functions are accessed only by IOT instructions. For example, interrupt enable and disable are IOT instructions: _ _ _ _ _ _ _ _ _ _ _ _ |1|1|0|_|_|_|_|_|_|_|_|_| |0 0 0 0 0 0|0 0 1 - ION - interrupts turn on |0 0 0 0 0 0|0 1 0 - IOF - interrupts turn off An interrupt is requested when any device raised its flag. The console master clear switch resets all flags and disables interrupts. In effect, an interrupt is a JMS instruction to location zero, with the side effect of disabling interrupts. The interrupt service routine is expected to test the device flags and perform the operations needed to reset them, and then return using ION immediately before the indirect return JMP. The effect of ION is delayed so that interrupts are not enabled until after the JMP. The instructions controlling the optional memory management unit are also IOT instructions. This unit allows the program to address up to 32K of main memory by adding a 3 bit extension to the memory address. Two extensions are available, one for instruction fetch and direct addressing, the other for indirect addressing. A wide variety of operations are available through the OPR microcoded instructions: _ _ _ _ _ _ _ _ _ _ _ _ Group 1 |1|1|1|0|_|_|_|_|_|_|_|_| 1 - CLA - clear AC 1 - CLL - clear the L bit 1 - CMA - ones complement AC 1 - CML - complement L bit 1 - IAC - increment 1 0 0 - RAR - rotate right 0 1 0 - RAL - rotate left 1 0 1 - RTR - rotate right twice 0 1 1 - RTL - rotate left twice In general, the above operations can be combined by oring the bit patterns for the desired operations into a single instruction. If none of the bits are set, the result is the NOP instruction. When these operations are combined, they operate top to bottom in the order shown above. The exception to this is that IAC cannot be combined with the rotate operations on some models, and attempts to combine rotate operations have different effects from one model to another (for example, on the PDP-8/E, the rotate code 001 means swap 6 bit bytes in the accumulator, while previous models took this to mean something like "shift neither left nor right 2 bits"). _ _ _ _ _ _ _ _ _ _ _ _ Group 2 |1|1|1|1|_|_|_|_|_|_|_|0| 1 0 - SMA - skip on AC < 0 \ 1 0 - SZA - skip on AC = 0 > or group 1 0 - SNL - skip on L /= 0 / 0 0 0 1 - SKP - skip unconditionally 1 1 - SPA - skip on AC >= 0 \ 1 1 - SNA - skip on AC /= 0 > and group 1 1 - SZL - skip on L = 0 / 1 - CLA - clear AC 1 - OSR - or switches with AC 1 - HLT - halt The above operations may be combined by oring them together, except that there are two distinct incompatible groups of skip instructions. When combined, SMA, SZA and SNL, skip if one or the other of the indicated conditions are true (logical or), while SPA, SNA and SZL skip if all of the indicated conditions are true (logical and). When combined, these operate top to bottom in the order shown; thus, the accumulator may be tested and then cleared. Setting the halt bit in a skip instruction is a crude but useful way to set a breakpoint for front-panel debugging. If none of the bits are set, the result is an alternative form of no-op. A third group of operate microinstructions (with a 1 in the least significant bit) deals with the optional extended arithmetic element to allow such things as hardware multiply and divide, 24 bit shift operations, and normalize. These operations involve an additional data register, MQ or multiplier quotient, and a small step count register. On the PDP-8/E and successors, MQ and the instructions for loading and storing it were always present, even when the EAE was absent, and the EAE was extended to provide a useful variety of 24 bit arithmetic operations. ------------------------------ Subject: What does PDP-8 assembly language look like? There are many different assemblers for the PDP-8, but most use a compatible basic syntax; here is an example: START, CLA CLL / Clear everything TAD X / Load X AND I Y / And with the value pointed to by Y DCA X / Store in X HLT / Halt X, 1 / A variable Y, 7 / A pointer Note that labels are terminated by a comma, and comments are separated from the code by a slash. There are no fixed fields or column restrictions. The "CLA CLL" instruction on the first line is an example of the microcoding of two of the Group 1 operate instructions. CLA alone has the code 7200 (octal), while CLL has the code 7100; combining these as "CLA CLL" produces 7300. As a general rule, except when memory reference instructions are involved, the assembler simply ors together the values of all blank separated fields between the label and comment. Indirection is indicated by the special symbol I in the operand field, as in the third line of the example. The typical PDP-8 assembler has no explicit notation to distinguish between page zero and current page addresses. Instead, the assembler is expected to note the page holding the operand and automatically generate the appropriate mode. If the operand is neither in the current page nor page zero, some assemblers will raise an error, others will automatically generate an indirect pointer to the off-page operand; this should be avoided because it only works for directly addressed off-page operands, and only when the memory management unit is not being used to address a data field other than the current instruction field. Note, in the final two lines of the example, that there is no "define constant" pseudo-operation. Instead, where a constant is to be assembled into memory, the constant takes the place of the op-code field. The PDP-8 has no immediate addressing mode, but most assemblers provide a notation to allow the programmer to ignore this lack: TAD (3) / add 3, from memory on the current page. TAD [5] / add 5, from memory on page zero. JMP I (LAB) / jump indirect through the address of LAB. Assemblers that support this automatically fill the end of each page with constants defined in this way that have been accumulated during the assembly of that page. Note that the variants "(3" and "[5" (with no closing parentheses) are usually allowed but the use of this sloppy form is discouraged. Furthermore, the widely used PAL8 assembler interprets the unlikely operand "(3)+1" as being the same as "(3+1)". Arithmetic is allowed in operand fields and constant definitions, with expressions evaluated in strict left-to-right order, as: TAD X+1 / add the contents of the location after X. TAD (X-1) / add the address of the location before X. Other operators allowed include and (&), or (!), multiply (^) and divide (%), as well as a unary sign (+ or -). Unfortunately, one of the most widely used assemblers, PAL8, has trouble when unary operators are mixed with multiplication or division. Generally, only the first 6 characters of identifiers are significant and numeric constants are evaluated in octal. Other assembly language features are illustrated below: / Comments may stand on lines by themselves / Blank lines are allowed *200 / Set the assembly origin to 200 (octal) NL0002= CLA CLL CML RTL / Define new opcode NL0002. NL0002 / Use new opcode (load 0002 in AC) JMP .-1 / Jump to the previous instruction X1= 10 / Define X1 (an auto-index register address) LETA= "A / Define LETA as 000011000001 (ASCII A) TAD I X1 / Use autoindex register 1 IAC; RAL / Multiple instructions on one line $ / End of assembly The assembly file ends with a line containing a $ (dollar sign) not in a comment field. The $, * and = syntax used by most PDP-8 assemblers replaces functions performed by pseudo-operations on many other assemblers. In addition, PAL8, the most widely used PDP-8 assembler supports the following pseudo-operations: DECIMAL / Interpret numeric constants in base 10 OCTAL / Interpret numeric constants in base 8 EJECT / Force a page eject in the listing XLIST / Toggle listing XLIST N / Turn on listing if N=0, off if N=1 PAGE / Advance location counter to next page PAGE N / Set location counter start of page N FIELD N / Assemble into extended memory field N TEXT "STR" / Pack STR into consecutive 6 bit bytes ZBLOCK N / Allocate N words, initialized to zero IFDEF S / Assemble C if symbol S is defined IFNDEF S / Assemble C if symbol S is not defined IFZERO E / Assemble C if expression E is zero IFNZRO E / Assemble C if expression E is not zero FIXMRI OP= VAL / Define OP as memory reference instruction Conditonally assembled code must be enclosed in angle brackets. The enclosed code may extend over multiple lines and, because different assemblers treat comments within conditionals differently, the closing bracket should not be in a comment and any brackets in comments should be balanced. ------------------------------ Subject: What character sets does the PDP-8 support? From the beginning, PDP-8 software has generally assumed that textual I/O would be in 7 bit ASCII. Most early PDP-8 systems used teletypes as console terminals; as sold by DEC, these were configured for mark parity, so most older software assumes 7 bit ASCII, upper case only, with the 8th bit set to 1. On output, lines are generally terminated with both CR and LF; on input, CR is typically (but not always) the line terminator and LF is typically ignored. In addition, the tab character (HT) is generally allowed, but software support output of text containing tabs varies. One difficulty with much PDP-8 software is that it bypasses the device handlers provided by the operating system and goes directly to the device. This results in very irregular device support, so that, for example, control-S and control-Q work to start and stop output under OS/8, but the OS/8 PAL assembler ignores them when reporting errors. Most of the better engineered PDP-8 software tends to fold upper and lower case on input, and it ignores the setting of the 8th bit. Older PDP-8 software will generally fail when presented with lower case textual input (this includes essentially all OS/8 products prior to OS/278 V1). Internally, PDP-8 programmers are free to use other character sets, but the "X notation provided by the assembler encourages use of 7 bit ASCII with the 8th bit set to 1, and the TEXT pseudo-operation encourages the 6 bit character set called "stripped ASCII". To map from upper-case-only ASCII to stripped ASCII, each 8 bit character is anded with octal 77 and then packed 2 characters per word, left to right. Many programs use a semi-standard scheme for packing mixed upper and lower case into 6 bit TEXT form; this uses ^ to flip from upper to lower case or lower to upper case, % to encode CR-LF pairs, and @ (octal 00) to mark end of string. Note that this scheme makes no provision for encoding the %, ^ and @ characters, nor does it allow control characters other than the CR-LF pair. The P?S/8 operating system supports a similar 6 bit text file format, where upper and lower case are folded together, tabs are stored as _ (underline), end-of-line is represented by 00, padded with any nonzero filler to a word boundary, and end of file is 0000. Files under the widely used OS/8 system consist of sequences of 256 word blocks. When used for text, each block holds 384 bytes, packed 3 bytes per pair of words as follows: aaaaaaaa ccccaaaaaaaa bbbbbbbb CCCCbbbbbbbb ccccCCCC Control Z is used as an end of file marker. Because most of the PDP-8 system software was originally developed for paper tape, binary object code is typically stored in paper-tape image form using the above packing scheme. ------------------------------ Subject: What different PDP-8 models were made? The total sales figure for the PDP-8 family is estimated at over 300,000 machines. Over 7000 of these were sold prior to 1970. During the PDP-8 production run, a number of models were made, as listed in the following table. Of these, the PDP-8/E is generally considered to be the definitive machine. If the PDP-8 is considered to be the Model T of the computer industry, perhaps the PDP-8/E should be considered to be the industry's Model A. MODEL DATES SALES COST TECHNOLOGY REMARKS PDP-5 63-67 116 Transistor PDP-8 65-69 1450 $18,500 Transistor LINC-8 66-69 142 $38,500 Transistor PDP-8/S 66-70 1024 $10,000 Transistor Very slow PDP-8/I 68-71 3698 $12,800 TTL PDP-8/L 68-71 3902 $8,500 TTL Scaled down 8/I PDP-12 69-73? 3500? $27,900 TTL Followup to LINC-8 PDP-8/E 70-78 >10K? $7,390 TTL MSI Omnibus PDP-8/F 72-78? >10K? <$7K TTL MSI Omnibus Based on 8/E CPU PDP-8/M 72-78? >10K? <$7K TTL MSI Omnibus OEM version of 8/F PDP-8/A 75-84? >10K? $1,317 TTL LSI Omnibus New CPU or 8/E CPU VT78 78-80 <$10K Intersil 6100 Workstation DECmate I 80-84 Harris 6120 Workstation DECmate II 82-86 $1,435 Harris 6120 Workstation DECmate III 84-90 $2,695 Harris 6120 Workstation DECmate III+85-90 Harris 6120 Workstation Additional information is available in part two of this FAQ, where all known models of the PDP-8, along with variants, alternate marketing names, and other peculiarities are given. The last years of the PDP-8 family were dominated by the PDP-8 compatible microprocessor based VT78 and DECmate workstations. DEC also used the Harris 6120 microprocessors in many peripheral controllers for the PDP-11 and PDP-15. While all of the earlier PDP-8 systems were open architecture systems, the DECmates had closed architectures with an integrated console terminals and limited peripheral options. The following PDP-8 compatible or semi-compatible machines were made and sold by others; very little is known about many of these: MODEL DATE MAKER, NOTES MP-12 6? Fabritek (a surviving example runs FOCAL). TPA 68? Hungarian, a PDP-8/L clone, ran FOKAL Electrotechnica-100I ? Yugoslavian, a PDP-8/I clone or OEM label. Saratov-2 ? Russian, a slow clone, perhaps PDP-8/S Voronezh ? Russian, another PDP-8/? clone SPEAR u-LINC 100? SPEAR, Inc, Waltham Mass (a LINC clone!) SPEAR u-LINC 300? SPEAR, Inc, Waltham Mass (a LINC clone!) DCC-112 70-71 Digital Computer Controls DCC-112H 71 Digital Computer Controls 6100 Sampler 7? Intersil, their IM6100 promotional kit Intercept I 7? Intersil, based on IM6100 Intercept Jr 7? Intersil, based on IM6100 PCM-12 7? Pacific CyberMetrix, based on Intercept bus PCM-12A 7? Pacific CyberMetrix, fixed to clock at 4MHz SBC-8 84-88 CESI, Based on IM6120, SCSI bus ------------------------------ Subject: What about the LINC/8 and PDP-12? Wesley Clark, then at Lincoln Labs, developed the LINC, or Laboratory INstrumentation Computer, as a personal laboratory computer in the early 1960's. He developed it in response to the needs of Mary Brazier, a neurophysiologist at MIT who needed better laboratory tools. Over 24 LINC systems were built by customers before late 1964 when DEC began selling a commercial version (see Computers and Automation, Nov. 1964, page 43). By the time DEC introduced the LINC-8, 43 LINC systems had been installed (see Computers and Automation, Mar. 1966, page 34). When Lincoln Labs decided that the LINC did not fit their mission, a group at the the National Institute of Health funded an experiment to see if the LINC would be a productive tool in the life sciences. As a result of this project, 12 LINCs were built and debugged, each by its eventual user. The LINC was the first 12 bit minicomputer built using DEC hardware. Like the PDP-5 and other early DEC computers, it was built with system modules, DEC's first family of logic modules. Along with the CDC 160, it paved the way for the PDP-5 and PDP-8. When compared with the PDP-8, the LINC instruction set was not as well suited for general purpose computation, but the common peripherals needed for lab work such as analog-to-digital and digital-to-analog converters were all bundled into the LINC system. Users judged it to be a superb laboratory instrument. One of the major innovations introduced with the LINC was the LINCtape. These tapes could be carelessly pocketed or dropped on the floor without fear of data loss, and they allowed random access to data blocks. DEC improved on this idea slightly to make their DECtape format, and DECtape was widely used with all DEC computers made in the late 1960's and early 1970's. The motives behind the development of LINCtape were the same motives that led IBM to develop the floppy disk almost a decade later, and in fact, DECtape survived as a widely used medium until DEC introduced the RX01 8 inch floppy disk drive around 1975, and even after this, DECtape was only slowly phased out. Within a year of the introduction of the PDP-8, DEC released the LINC-8, a machine that combined a PDP-8 with a LINC in one package. The success of the LINC-8 led DEC to re-engineer the machine using TTL logic in the late 1960's; the new version was originally to be called the LINC-8/I, but it was sold as the PDP-12. Both the LINC-8 and the PDP-12 had impressive consoles, with separate sets of lights and switches for the LINC and PDP-8 halves. The success of the LINC-8 also led to the development of a clone, the SPEAR micro-LINC. This machine used Motorola MECL integrated circuits and was available for delivery in (June 1965? this date must be wrong!). The LINC-8 and PDP-12 could run essentially any PDP-8 or LINC program, with the exception of the few programs that relied on the primitive interrupt structure of the original LINC architecture; on the LINC-8, all interrupts were handled by the PDP-8 side of the hardware. Because the LINC-8 and PDP-12 had instructions for switching between modes, a new body of software was developed that required both modes. One feature of LINC and LINC-8 software is the common use of the graphic display for input-output. These machines were some of the first to include such a display as a standard component, and many programs used the knobs on the analog to digital converter to move a cursor on the display in the way we now use a mouse. Various versions of LAP, the Linc Assembly Program, were the dominant assemblers used on the LINC. WISAL (WISconson Assembly Language) or LAP6-W was the version of this assembler that survived to run on the PDP-12. Curiously, this includes a PDP-8 assembler written in LINC code. LAP6-DIAL (Display Interactive Assembly Language) evolved from this on the PDP-12 to became the dominant operating system for the PDP-12. The 8K version of this is DIAL MS (Mass Storage), even if it has only two LINCtape drives. These were eventually displaced by the OS/8 variant known as OS/12. ------------------------------ Subject: Where can I get a PDP-8 today? The IM6100 chip is still available (Electronic Expediters, (818)781-1910 (in North America) listed them at US$23.50 each as of 10/1994), and CESI may still make their clone, for a high price, but you can't buy a new DEC PDP-8. There are quite a few PDP-8 machines to be found in odd places on the used equipment market. They were widely incorporated into products such as computer controlled machine tools, X-ray diffraction machines, and other industrial and lab equipment. Many of them were sold under the EduSystem marketing program to public schools and universities, and others were used to control laboratory instrumentation. After about 1976, Reuters bought as many as 10,000 OMNIBUS based machines per year, with perhaps 2000 per year going to other customers. If you can't get real hardware, you can get emulators. Over the years, many PDP-8 emulators have been written; the best of these are indistinguishable from the real machine from a software prespective, and on a modern high-speed RISC platform, these frequently outperform the hardware they are emulating. An emulator is available from DECUS, catalog number RB0128; This and other emulators are available from: ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/emulators ftp://ftp.cs.uiowa.edu/public/jones/pdp8/emulator.txt.Z Finally, you can always build your own. The textbook "The Art of Digital Design," second edition, by Franklin Prosser and David Winkel (Prentice-Hall, 1987, ISBN 0-13-046780-4) uses the design of a PDP-8 as a running example. Many students who have used this book were required to build working PDP-8 systems as lab projects. ------------------------------ Subject: Where can I get PDP-8 documentation? The key documents published by DEC describing each model of the PDP-8 are all out of print, and DEC was in the habit of printing much of their documentation on newsprint with paperback bindings, which is to say, surviving copies tend to be yellow and brittle. DEC distributed huge numbers of catalogs and programming handbooks in this inexpensive paperback format, and these circulate widely on the second-hand market. When research laboratories and electronics shops are being cleaned out, it is still common to find a few dusty, yellowed copies of these books being thrown out. Douglas Jones has made a small number of bound photocopies of DEC's 1973 introduction to programming, perhaps the definitive introduction to the PDP-8, and the other early DEC handbooks need similar treatment before they all crumble. Some PDP-8 refernce material has been transcribed into Hypertext format and is available over WWW from: http://www.cs.uiowa.edu/~jones/pdp8/index.html Maintenance manuals are harder to find, but more valuable. If you need one, you usually need to find someone willing to photocopy one of the few surviving copies. DEC has been friendly to collectors, granting fairly broad letters of permission to reprint obsolete documentation, and the network makes if fairly easy to find someone who has the documentation you need and can get copies. The most difficult to copy material is the large prints, many of which would be quite useful if photoreduced, but this is expensive. ------------------------------ Subject: What operating systems were written for the PDP-8? A punched paper-tape library of stand-alone programs was commonly used with the smallest (diskless and tapeless) configurations from the beginning up through the mid 1970's. This included a paper-tape based text editor, the PAL III and MACRO-8 assembler, and a FORTRAN compiler, as well as a library of support routines. Many paper tapes from this library survive to the present at various sites! The minimum configuration expected by these tapes is a CPU with 4K memory and a teletype ASR 33 with paper tape reader and punch. Note that much of this paper-tape-based software is based on memory-use and I/O conventions that are incompatible with later disk-based systems. The DECtape Library System was a DECtape oriented save and restore system that was available from the start. The resident portion of this system occupies only 17 words of memory (7600-7625 octal), and it allowed saving and restoring absolute core images as named files on a reel of DECtape. Initially, program development was still done with paper tape, and only executable memory images were stored on DECtape, but eventually, a limited DECtape-based text editor was introduced, along with a DECtape based assembler. The 4K Disk Monitor System provided slightly better facilities. This supported on-line program development and it worked with any device that supported 129 word blocks (DECtape, the DF32 disk, or the RF08 disk). It was quite slow, but it also used very little of the available memory. MS/8 or the R-L Monitor System, was developed starting in 1966 and submitted to DECUS in 1970. This was a disk oriented system, faster than the above, with tricks to make it run quickly on DECtape based systems. POLY BASIC was a BASIC only system submitted to DECUS and later sold by DEC as part of its EduSystem marketing program. EduSystem 25 Basic is available from: ftp://nickel.ucs.indiana.edu/pub/DEC/PDP8/Langs/Edu25Basic P?S/8 was developed starting in 1971 from an MS/8 foundation. It runs on minimal PDP-8 configurations, supports somewhat device independant I/O and requires a random-access device for the file system (DECtape is random-access!). P?S/8 runs compatibly on most PDP-8 machines including DECmates, excepting only the PDP-8/S and PDP-5. P?S/8 is still being developed! Richard F. Larry developed a system called the Fully Upward Compatible Keyboard Monitor; and between a Wednesday and the following Friday, a prototype was up and running from DECtape. The original intention of this project was to build a programming environment for the PDP-8 that looked like TOPS-10 on the PDP-10. A year later, this was released as Programming System/8 (or PS/8), and then renamed OS/8 in 1971 because Eli Glaser (a salesman from Long Island) said he could sell more systems with an operating system than with a programming system, and because, by renaming the system, DEC could increase the price despite Nixon's wage-price freeze. OS/8, developed in parallel with P?S/8, became the main PDP-8 programming environment sold by DEC. The minimum configuration required was 8K words and a random-access device to hold the system. For some devices, OS/8 requires 12K. There are a large number of OS/8 versions that are not quite portable across various subsets of the PDP-8 family. OS/8 V3D was renamed OS/78 (to match the VT78), and by the time OS/78 V3 was released, support for Omnibus machines was no longer important. OS/78 V4 was developed for the DECmate I, and the name OS/278 used for the versions released with later DECmate machines. These have unnecessary incompatabilities with earlier versions of OS/8. OS/278 and related material is available from DECUS as catalog item 800941, or from: ftp://ftp.telebit.com/pub/pdp8/os278 ftp://ftp.update.uu.se/pub/pdp8 ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/os8 OS8 (no slash) may still be viable. It requires 8K of main memory, an extended arithmetic unit, and DECtape hardware. Unlike most PDP-8 operating systems, it uses a directory structure on DECtape compatible with that used on the PDP-10. TSS/8 was developed in 1968 as a timesharing system. It required a minimum of 12K words of memory and a swapping device. It was the standard operating system on the EduSystem 50 which was sold to many small colleges and large public school systems. Each user gets a virtual 4K PDP-8; many of the utilities users ran on these virtual machines were only slightly modified versions of utilities from the Disk Monitor System or paper-tape environments. Other timesharing systems developed for the PDP-8 include MULTI-8, ETOS, MULTOS, and OMNI-8; some of these required nonstandard memory management hardware. By the mid 1970's, some of these were true virtual machine operating systems in the same spirit as IBM's VM-370; they typically supported some version of OS/8 running on a 32K virtual PDP-8 assigned to each user. Some could support different user operating systems on each virtual machine, others supported addressing of more than 4K for data, but limited code to field zero of a process's virtual memory. The source for MULTOS is available from: ftp://ftp.update.uu.se/pub/pdp8/multos8 CAPS-8 was a cassette based operating system supporting PAL and BASIC. There are OS/8 utilities to manipulate CAPS-8 cassettes, and the file format on cassette is compatible with a PDP-11 based system called CAPS-11. RTS/8 was a real-time system developed by DEC, developed from an earlier system, SRT8, dating back to at least 1974. Curiously, even the last versions of RTS/8 continued to support paper-tape and DECtape. Source code for most of the versions of RTS and SRT are available from: ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/rts8 WPS was DEC's word processing system, developed for the 8/E with a VT50 terminal with special WPS keycaps replacing the standard keycaps, and widely used on the 1980's vintage machines. It was heavily promoted on the VT-78, and when the DECmates came out, DEC began to suppress knowledge that DECmates could run anything else. WPS-11 was a curious distributed system using a PDP-11 as a file server for a cluster of VT-78 WPS systems. DECmate/WPS Version 2.3 is available from DECUS for the DECmate II and DECmate III under the catalog entry DM0114. COS-310, DEC's commercial operating system for the PDP-8, supported the DIBOL language. COS-310 was a derivative of MS/8 and OS/8, but with a new text file format. The file system is almost the same as OS/8, but dates are recorded differently, and a few applications can even run under both COS and OS/8. COS was the last operating system other than WPS promoted by DEC for the DECmates. ------------------------------ Subject: What programming languages are supported on the PDP-8 The PAL family of assembly languages, particularly PAL III and PAL8 are as close to a standard assembly language as can be found for the PDP-8. These produce absolute object code and there are versions of PAL for minimally configured machines, although these have severe symbol table limitations. Cross assemblers that are somewhat compatable with PAL can be obtained from: ftp://ftp.cs.uiowa.edu/public/jones/pdp8/pal.c.Z ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/emulators/gray MACRO-8 was DEC's first macro assembly language for the PDP-8, but it was rarely used outside the paper-tape environment. MACREL and SABR are assembly languages that produce relocatable output. SABR is the final pass for the ALICS II FORTRAN compiler (developed by ICS), and MACREL was developed in (unfulfilled) anticipation of similar use. MACREL was heavily used by the DECmate group at DEC. MACREL is available from ftp://ftp.update.uu.se/pub/pdp8/os8 There was also RALF, the relocatable assembler supporting RTPS FORTRAN, and FLAP, an absolute assembler derived from RALF. Both SABR and RALF/FALP are assemblers that handle their intended applications but have quirky and incompatible syntax. A subset of FORTRAN was supported on both the PDP-5 and the original PDP-8. Surviving documentation describes a DEC compiler from 1964 and a compiler written by Information Control Systems from 1968. The latter, ALICS II FORTRAN, was originally a paper tape based compiler, but it forms the basis of the OS/8 8K FORTRAN compiler, and was also adapted to the Disk Monitor System (the latter version had overlay support that was never carried forward into more modern systems). RTPS FORTRAN required 8K and a floating point processor; it had real-time extensions and was a full implementation of FORTRAN IV (also known as ANSI FORTRAN 66). OS/8 F4 is RTPS FORTRAN stripped of the requirement for hardware floating point (if the hardware is missing, it uses software emulation). A version of FORTRAN is available from ftp://ftp.update.uu.se/pub/pdp8/os8 FOCAL, an interpretive language comparable to BASIC, was available on all models of the family, including the PDP-5 and PDP-8/S. Versions of FOCAL run under OS/8, P?S/8 and other systems, and there were many special purpose overlays for FOCAL developed by DEC and by various users. DEC's later FOCAL releases for the PDP-8 included code to deliberately introduce subtle bugs when run on a DCC 112 computer! Various versions of FOCAL are available from: ftp://nickel.ucs.indiana.edu/pub/DEC/PDP8/Langs/Focal Many versions of BASIC were also available, from DEC and other sources. DEC BASIC was widely used on PDP-8 systems sold under the EduSystem marketing program. A paper-tape version was available that ran in 4K and was compatible with disk based systems, versions were developed for OS/8 and TSS/8, an 8K stand-alone time-sharing version was available, and there were others. EduSystem 25 Basic is available from: ftp://nickel.ucs.indiana.edu/pub/DEC/PDP8/Langs/Edu25Basic DIBOL was DEC's attempt at competing with COBOL in the commercial arena. It was originally implemented under MS/8 but most versions were sold to run under the COS operating system. Algol was available from a fairly early date. One version is available from: ftp://nickel.ucs.indiana.edu/pub/DEC/PDP8/Langs/Algol At least two Pascal compilers were developed for the PDP-8. One was a Pascal-S interpreter, written in assembler, the other was a Pascal-P compiler with a P-code interpreter written in assembler. A LISP interpreters was written for the PDP-8; the original version ran in 4K (originally written in Germany?); a disassembled and commented version of this was the basis of expanded versions that eventually could utilize up to 16K. One version of LISP is available from: ftp://nickel.ucs.indiana.edu/pub/DEC/PDP8/Langs/Lisp A Pascal S interpreter, requiring a 28K PDP-8/E configuration, is available from: ftp://nickel.ucs.indiana.edu/pub/DEC/PDP8/Langs/Pascal POLY SNOBOL was a version of SNOBOL that was somewhere between Griswold's definitions of SNOBOL 3 and SNOBOL 4. TECO, the text editor, is available, and is also a general purpose language, and someone is working on a PDP-8 C. The story of TECO on the PDP-8 is convoluted. Russ Ham implemented TECO under his OS8 (without a slash) system. This version of TECO was pirated by the Oregon Museum of Science and Industry (OMSI), where the system was ported to PS/8. Richard Lary and Stan Rabinowitz made it more compatible with other versions of TECO, and the result of this work is the version distributed by DECUS (catalog number 110450 is the manual). RT-11 TECO for the PDP-11 is a port of this code. DECUS also lists the PAGE8 language (catalog numbers 800936), the VISTA editor (catalog number 800938), and the ICE text editor (catalog number 800939). ------------------------------ Subject: Where can I get PDP-8 software? DEC is still making computers, but they've largely forgotten about the PDP-8. The main DEC WWW server is http://www.digital.com/ DECUS, the DEC User Society, is still alive and well, and their submission form still lists PAL8 and FOCAL as languages in which they accept submissions! The DECUS library catalog is available on-line at decus.org; www access is through gopher.decus.org or http://www.decus.org/ To quote the README file from the DECUS on-line catalog, "Items from older DECUS Library catalogs are still also available (provided their media can still be read), but machine readable catalog information is not available for these." Direct questions by E-mail to INFORMATION@DECUS.ORG. The following anonymous FTP sites contain publically accessable archives of PDP-8 software and other information: ftp://ftp.telebit.com/pub/pdp8 ftp://ftp.update.uu.se/pub/pdp8 ftp://nickel.ucs.indiana.edu/pub/DEC/PDP8 ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8 The latter archive also maintains an archive of traffic in alt.sys.pdp8 in the directory ...pdp8/usenet and an archive of traffic in the pdp8-lovers mailing list in .../pdp8/pdp8-lovers. The archive at Indiana contains source code for many PDP-8 compilers and interpreters, as well as common utilities and games. ------------------------------ Subject: Where can I get additional information? The file WHAT-IS-A-PDP8, by Charles Lasner contains considerable additional information; this file is available by ftp from: ftp://ftp.telebit.com/pub/pdp8/WHAT-IS-A-PDP8 This file gives details of every PDP-8 model including the small quirks and incompatabilities that (to be generous) allow software to determine which model it is running on. These quirks also make it all too easy for careless programmers to write almost portable software with very obscure bugs. The mailing list pdp8-lovers@ai.mit.edu reaches a number of PDP-8 owners and users, not all of whom have USENET feeds. The USENET newsgroup alt.sys.pdp8 needs to be gatewayed to this mailing list. Many "archival" books have included fairly complete descriptions of the PDP-8; among them, "Computer Architecture, Readings and Examples" by Gordon Bell and Allen Newell is among the most accurate and complete (but difficult to read). ------------------------------ Subject: What use is a PDP-8 today? What use is a Model T today? Collectors of both come in the same basic classes. First, there are antiquarians who keep an old one in the garage, polished and restored to new condition but hardly ever used. Once a year, they warm it up and use it, just to prove that it still works, but they don't make much practical use of it. PDP-8 systems maintained by antiquarians are frequently in beautiful shape. Antiquarians worry about dust, chipped paint, and missing switches, and they establish newsgroups and mailing lists to help them locate parts and the advice needed to fix their machines. In the second class are those who find old machines and soup them up, replacing major parts to make a hotrod that only looks like the original from the outside, or keeping the old mechanism and putting it to uses that were never intended. Some PDP-8 owners, for example, have built PDP-8 systems with modern SCSI disk interfaces! There is serious interest in some quarters in constructing an omnibus board that would support an IDE disk of the variety that was mass-produced for the IBM PC/AT. Last, there are the old folks who still use their old machines for their intended purposes long after any sane economic analysis would recommend such use. If it ain't broke, don't fix it, and if it can be fixed, why bother replacing it? Both Model T Fords and the classic PDP-8 machines are simple enough that end users can maintain and repair them indefinitely. All you need to keep a vintage -8 running are a stock of inexpensive silicon diodes and a stock of 2N3639B or better, 2N3640 transistors. Unlike most modern personal computers, PDP-8 systems were routinely sold with complete maintenance manuals; these included schematic diagrams, explanations of not only how to use the devices, but how they are built, and suggestions to those considering building their own peripherals. Compared with many so-called "open systems" of today, the PDP-8 was far better documented and far more open. Preservation of the PDP-8 has proven to be of immense practical value in defending against the rising tide of patents in the area of interactive graphics. For example, when Magnavox sued Nintendo for half a billion dollars, a documented copy of a ping pong game, written on a LINC back in the early 1960's, was crucial to the proof that computer games predated the Magnavox patent by over 5 years. The fact that this can be run today on a surviving LINC-8 makes demonstrating this proof far easier than if the only surviving relic was a dusty listing. Finally, the PDP-8 is such a minimal machine that it is an excellent introduction to how computers really work. Over the years, many students have built complete working PDP-8 systems from scratch as lab projects, and the I/O environment on a PDP-8 is simple enough that it is a very appropriate environment for learning operating system programming techniques. ------------------------------ Subject: Who's Who? C. Gordon Bell is generally credited with the original design of the PDP-8. He was also involved with recommending what became the PDP-11 when that design was competing with the design that probably became the NOVA, and as vice president of research, he oversaw the development of the DEC VAX family. Alan Kotok worked with Bell in working up the original specifications of the PDP-8. Ben Gurley designed most of the big DEC machines, starting with the PDP-1. The actual design work on the -8, however, was done by Ed deCastro, who later founded Data General to build the Nova. Ken Olson ran DEC from the beginning. Ed Yourdon, who later became well known as a programming methodology guru, helped hack up the PAL III assembler for the -8 from PAL II. Richard Merrill invented FOCAL and wrote the original (1968) and classic FOCAL-69 interpreters for the PDP-8. He also did early translations of the interpreter to PDP-7/PDP-9 code and perhaps the earliest PDP-11 version. In addition, he wrote the EDIT-8 paper-tape based text editor based on the FOCAL built-in text editor. Richard F. Lary developed OS/8, with help from Ed Friedman and another programmer named Paul, under the management of Chuck Conley. Charles Lasner developed P?S/8, and he is widely known as a leader in the movement to preserve these historic machines. He created the alt.sys.pdp8 newsgroup. Wesley Clark developed the LINC while working at Lincoln Labs; this was the first 12 bit minicomputer built with DEC parts. Mary Allen Wilkes Clark developed the early LAP programs for the LINC. Douglas W. Jones wrote this FAQ, but prior to the summer of 1992, he'd never used a PDP-8. He has also written a report on how to photocopy and archivally bind ailing paperback books such as DEC's handouts, a PAL-like cross assembler in C, and a UNIX-based PDP-8 emulator. ------------------------------ End of PDP-8 Frequently Asked Questions (posted every other month) ****************************************************************** Article 1116 of alt.sys.pdp8: Path: bigblue.oit.unc.edu!concert!theo!news-server.ncren.net!taco.cc.ncsu.edu!gatech!swrinde!pipex!uunet!news.uiowa.edu!news From: jones@cs.uiowa.edu (Douglas W. Jones) Newsgroups: alt.sys.pdp8,alt.answers,news.answers Subject: PDP-8 Summary of Models and Options (posted every other month) Followup-To: alt.sys.pdp8 Date: 8 Dec 1994 08:08:08 GMT Organization: Computer Science, University of Iowa, Iowa City, Iowa, USA Lines: 1317 Approved: news-answers-request@MIT.Edu Distribution: world Expires: 8 Feb 1995 08:08:08 GMT Message-ID: <3c7boj$9du@nexus.uiowa.edu> NNTP-Posting-Host: pyrite.cs.uiowa.edu Summary: Descriptions of all models of the DEC PDP-8 computer. Those posting to alt.sys.pdp8 should read this. Keywords: FAQ DEC PDP 8 Xref: bigblue.oit.unc.edu alt.sys.pdp8:1116 alt.answers:5909 news.answers:32285 Archive-name: dec-faq/pdp8-models Last-modified: Oct 11, 1994 Frequently Asked Questions about DEC PDP-8 models and options. By Douglas Jones, jones@cs.uiowa.edu (with help from many folks) Sites known to carry FTPable copies of this file: ftp://rtfm.mit.edu/pub/usenet/alt.sys.pdp8 ftp://ftp.uu.net/usenet/news.answers/dec-faq ftp://src.doc.ic.ac.uk:/pub/usenet/news.answers/alt.sys.pdp8 ftp://sunsite.unc.edu/pub/academic/computer-science/history/pdp-8/docs Automatic translations of this document to HTML format (as used by World Wide Web) are available from: http://www.cis.ohio-state.edu/hypertext/faq/usenet/dec-faq/top.html This posting conforms to RFC1153 USENET digest format (with exceptions due to the fact that it is not really a digest). The purpose of this document is to supplement the material in the primary "Frequently Asked Questions about the PDP-8" file with more detailed information about the hardware and options of the different models of the PDP-8 sold by DEC. Although this document is something of a history of the DEC PDP-8 family, the primary purpose of this document is as a guide and general outline to the PDP-8 models and options likely to be encountered by those involved in collecting and restoring such systems. Contents: What is a PDP-5? What is a PDP-8? What is a LINC-8? What is a PDP-8/S? What is a PDP-8/I? What is a PDP-8/L? What is a PDP-12? What is a PDP-8/E? What is a PDP-8/F? What is a PDP-8/M? What is a PDP-8/A? What is a VT78? What is a DECmate I? What is a DECmate II? What is a DECmate III? What is a DECmate III+? ---------------------------------------------------------------------- Subject: What is a PDP-5? Date of introduction: Aug 11, 1963, unveiled at WESCON. Date of withdrawal: early 1967. Total production run: 116. Price: $27,000 Technology: The PDP-5 was built with DEC System Modules, the original line of transistorized logic modules sold by DEC. The supply voltages were +10 and -15 volts, with logic levels of -3 (logic 1) and 0 (logic 0). Logic was packaged on boards that were about 4.75 inches high with each card mounted in a metal frame with a 22 pin edge connector. Input output devices were connected to the daisy-chained I/O bus using military-style armored cables and connectors. Use of toggle switches (as opposed to slide switches) on the front panel was another vestige of military-style design. Reason for introduction: This machine was inspired by the success of the CDC-160, Seymour Cray's 12 bit minicomputer, and by the success of the LINC, a machine that was built by DEC customers out of System modules. These demonstrated that there was a market for a small inexpensive computer, and from the start, DEC's advertisements were aimed at this market. "Now you can own the PDP-5 computer for what a core memory alone used to cost: $27,000", ran one 1964 ad. Reason for withdrawal: The PDP-8 outperformed the PDP-5, and did so for a lower price. Compatability: The core of the PDP-8 instruction set is present, but memory location zero is the program counter, and interrupts are handled differently. The Group 1 OPR rotate instructions cannot be combined with IAC or CMA; this limits the ability of the PDP-5 to support code from later models. The machine does not support 3 cycle data-break (DMA transfers using memory to hold buffer address and word-count information), so many later PDP-8 peripherals can not be used on the PDP-5. In addition, DMA transfers are not allowed outside the program's current 4K data field, severely limiting software compatability on systems with over 4K of memory where either interrupts or software initiated changes to the data field during a transfer would cause chaos. Standard configuration: CPU with 1K or 4K of memory (2K and 3K versions were not available). Peripherals: An extended arithmetic element (EAE) was available; this was an I/O device, using IOT instructions to evoke EAE operations. As a result, it was not compatable with the later PDP-8 EAEs. In addition, machines with the EAE option had a different front panel from those without. The type 552 DECtape control and type 555 dual DECtape transports were originally developed for the PDP-5 and contemporaneous DEC systems such as the PDP-6. After the PDP-8 was introduced, DEC offered a bus converter that allowed the PDP-5 to support standard PDP-8 negibus ueripherals, so long as they avoided using 3-cycle data break transfers. The standard 804 PDP-8 expander box was frequently sold as an upgrade to PDP-5 systems. Survival: Do any PDP-5 systems survive? ------------------------------ Subject: What is a PDP-8? Date of introduction: 1965 (Unveiled March 22, in New York). Date of withdrawal: 1968. Total production run: 1450. Also known as: Classic PDP-8 (to point out lack of a model suffix) Straight-8 (Again, points out the lack of a model suffix) PCP-88, an OEM label, used by Foxboro Corporation. Price: $18500 Technology: Mostly standard DEC R-series logic modules; these were originally discrete component transistor logic, but around the time the PDP-8 was introduced, DEC introduced the Flip Chip, a hybrid diode/resistor "integrated circuit" on a ceramic substrate. These could directly replace some of the discrete components on some logic modules, and DEC quickly began to refer to all R-series modules as flip-chip modules; they even advertised the PDP-8 as an integrated circuit computer. A typical flip-chip module, the R111, had three 2-input nand gates and cost $14, with no price change from 1965 to 1970. Some special dual height R-series modules were designed specifically for the PDP-8. S and B-series logic modules were also used; these are similar to their R-series cousins, but with different speed/fanout tradeoffs in their design. Some logic modules have trimmers that must be tuned to the context, making replacement of such modules more complex than simply swapping boards. As with the system modules used in the PDP-5, the supply voltages were +10 and -15 volts and the logic levels were -3 (logic 1) and 0 (logic 0). Logic was packaged on boards that were 2.5 inches wide by 5 inches long. The card edge connector had 18 contacts on 1/8 inch centers. Some double height cards were used; these had two card edge connectors and were 5 1/8 inches high. Machine wrapped wire-wrap technology was used on the backplane using 24-gauge wire. The "negibus" or negative logic I/O bus used -3 and 0 volt logic levels in 92 ohm coaxial cable, with 9 coaxial cables bundled per connector card and 6 bundles making up the basic bus. 5 (later 4) more bundles were required to support data-break (DMA) transfers. The total bus length was limited to 50 feet, and bus termination was generally kluged in with 100 ohm resistors clipped or wrapped into the backplane, although a bus terminator card was sometimes used. Some time after the first year of production, flat ribbon cable made of multiple coaxial cables was used, and later still, shielded flat stripline cable was used (but this cut the allowed bus length by a factor of two). Core memory was used, originally made by FERROXCUBE, with a 1.5 microsecond cycle time, giving the machine an add time of 3 microseconds. 4K of core occupied an aluminum box 6 inches on a side and needed numerous auxiliary flip-chips and for support, as well as an array of boards from the core vendor. It is worth noting that the PDP-8 was about as fast as was practical with the logic technology used; only by using tricks like memory interleaving or pipelining could the machine have been made much faster. Reason for introduction: This machine was inspired by the success of the PDP-5 and by the realization that, with their new Flip-Chip technology, DEC could make a table-top computer that could be powered by a single standard wall outlet; of course, adding any peripherals quickly increased the power requirement! Reason for withdrawal: The PDP-8/I was less expensive, and after initial production difficulties, it equalled the performance of the PDP-8. Compatability: This machine defines the core of the PDP-8 instruction set, but with restrictions that were lifted on later machines. The Group 1 OPR instruction IAC cannot be combined with any of the rotate instructions. If RAR and RAL or RTR and RTL are combined, the results are unpredictable (simultaneous set and reset of bits of AC results in metastable behavior). The IOT 0 instruction was used for the internal type 189 ADC, and not for the later CAF (clear all flags) instruction. As a result, if the ADC option was not present, IOT 6004 (or microcoded variants) would hang the machine. The SWP instruction (exchange AC and MQ) never works, even if the extended arithmetic element is present. This works on later models when the EAE is present, although it was only documented with the introduction of the PDP-8/E. Finally, the EAE lacks the SCL (shift count load) instruction that is present on later models. On machines with 8K or more, an attempt to change the data field to a non-existant field caused a bizarre double-indirect and skip instruction execution that must be accounted for in memory diagnostics. Standard configuration: The PDP-8 was sold as a CPU with 4K of memory, a 110 baud current loop teletype interface and an ASR 33 Teletype. In addition, the standard in-cabinet logic includes support for the full negibus interface, including data-break (DMA) transfers. Both a rack-mount model with rosewood trim and an elegant plexiglass enclosed table-top configuration were standard. Under the skin, the basic machine occupies a volume 33 inches high by 19 inches wide by 22 inches deep. The two halves of the backplane are mounted vertically, like the covers of a book, with the spine in back and circuit modules inserted from the two sides. Sliding the CPU out of the relay rack or removing the plexiglass covers allows the backplane to swung open to access the wires-wrap. Expandability: In-cabinet options include the type 182 extended arithmetic element (EAE), the type 183 memory extension control subsystem, and the type 189 low performance analog to digital converter (ADC). Prewired backplane slots were reserved for all of these. Expansion beyond 4K of memory requires rack space for the rack-mounted type 184 memory module; each such module adds one 4K field of memory, up to a maximum of 32K. The rack-mount CPU occupied a large part of one rack, allowing room for a single type 184 memory expansion module below the CPU; generally, a second rack was needed for added peripherals or memory. At the end of the production run, some PDP-8 systems were sold with PDP-8/I memory, allowing room for an additional 4K without need for an expansion chassis. These nonstandard machines were very difficult to maintain! Peripherals: At the time of introduction, the following negibus peripherals were offered. -- Type 750C high speed paper tape reader and control. -- Type 75E high speed paper tape punch and control. -- Type 138E analog to digital converter. -- Type 139E analog multiplexor. -- Type 34D oscilloscope display control (dual digital to analog). -- Type 350B incremental (CalComp) plotter control. -- Type 451 card reader and control. -- Type 450 card punch control for IBM Type 523 punch. -- Type 64 (later 645) Mohawk line printer and control. -- Type RM08 serial magnetic drum system (up to 256K words). -- Type 552 DECtape control (for type 555 DECtape drives). -- Type 57A magnetic tape control (IBM type 729 drive). -- Type 580 magnetic tape system. By 1966, the following peripherals had been added to the line: -- Type AA01A three-channel digital to analog converter. -- Type CR01C card reader control. -- Type TC01 DECtape control for up to 8 TU55 transports. -- Type 251 drum (8-256 tracks, 8 sectors/track, 128 words/sector). -- Type 645 line printer control. -- Type 680 data communications system (allows 64 teletypes). By 1967, the following peripherals had been added to the line: -- Type AF01 analog to digital converter and multiplexor. -- Type AX08 parallel digital input port. -- Type 338 Programmed Buffered Display (vector graphics). By 1968, the following new peripheral had been added: -- Type DF32 fixed head disk system (32K to 256K words). -- Type BE01 OEM version of the TC01 (no blinking lights). -- Type BE03 dual TU55 drive for the TC01 or BE01. Finally, as DEC abandoned the negibus, they introduced the DW08B negibus to posibus converter so newer posibus peripherals could be used on older negibus machines, and the DW08A posibus to negibus converter to allow use of old peripherals on new machines. Survival: Many classic PDP-8 systems survive to this day ------------------------------ Subject: What is a LINC-8? Date of introduction: 1966 (during or before March). Date of withdrawal: 1969 Total production run: 142. Price: $38,500 Technology: DEC Flip Chip modules, as in the PDP-8, with a LINC CPU partially reimplemented in Flip Chips and partially emulated with PDP-8 instructions. (The original LINC was built from the same System Modules used in the PDP-5.) Compatability: The PDP-8 part of the machine was identical to the PDP-8. Reason for withdrawal: The PDP-12 accomplished the same goals at a lower cost. Standard configuration: The combined PDP-8/LINC CPU, plus 4K of memory was central to the system. The set of peripherals bundled with the machine was impressive: -- An ASR 33 Teletype modified for the LINC character set. -- Two LINCtape drives. -- 8 analog to digital converter channels with knob inputs. -- Another 8 ADC channels with jack inputs. -- 6 programmable relay outputs, good up to 60 Hz. -- 1 Tektronix 560 oscilliscope, somewhat modified. The X and Y axis control for the scope came from DACs attached to the LINC's AC and MB registers, respectively. Expandability: In addition to standard PDP-8 peripherals, up to 3 additional pairs of LINCtape drives could be added, for a total of 8 drives. The design of the type 555 dual DECtape transport was based on that of the LINCtape drive. Up to 2 additional ranks of 8 ADC channels could be added. Remote oscilliscope could be added. Survival: One LINC-8 is known to be in operable condition today. ------------------------------ Subject: What is a PDP-8/S? Date of introduction: 1966 (Unveiled, Aug 23, WESCON, Los Angeles). Date of withdrawal: 1970. Total production run: 1024. Price: $10,000 Technology: DEC Flip Chip modules and core memory, as in the PDP-8. Unlike the PDP-8, the PDP-8/S memory module was mounted between a pair of quad-height single-width boards that plugged into the standard flip-chip sockets (this was sold separately as the H201 core memory unit, at $2000 for 4K by 13 bits). Reason for introduction: This machine was developed as a successful exercise in minimizing the cost of the machine. It was the least expensive general purpose computer made with second generation (discrete transistor) technology, and it was one of the smallest such machines to be mass produced (a number of smaller machines were made for aerospace applications). It was also incredibly slow, with a 36 microsecond add time, and some instructions taking as much as 78 microseconds. By 1967, DEC took the then unusual step of offering this machine for off the shelf delivery, with one machine stocked in each field office available for retail sale. Reason for withdrawal: The PDP-8/L vastly outperformed the PDP-8/S, and and it did so at a lower price. Compatability: The core of the PDP-8 instruction set is present, but there are a sufficient number of incompatabilities that, as with the PDP-5, many otherwise portable "family of 8" programs will not run on the PDP-8/S. Perhaps the worst incompatability is that the Group 1 OPR instruction CMA cannot be combined with any of the rotate instructions; as with the PDP-8, IAC also cannot be combined with rotate. Standard configuration: CPU with 4K of memory, plus PT08 110 baud current loop teletype interface and teletype. Both a rack-mount and table-top versions were sold (both 9" high by 19" wide by 20"? deep). The rack mount version included slides so it could be pulled out for maintenance. Expandability: The CPU supported the standard PDP-8 negibus, but I/O bandwidth was 1/5 that of the PDP-8. Thus, most, but not all PDP-8 peripherals could be used. A few DEC peripherals such as the DF32 came with special options such as interleaving to slow them down for compatability with the PDP-8/S. The speed problems were such that there was never any way to attach DECtape to this machine. Survival: Because they were so slow, PDP-8/S systems were quickly discarded as newer machines became available for comparable prices; thus, they are less common today than the Classic PDP-8, even though comparable numbers were made. A few survive in working condition. ------------------------------ Subject: What is a PDP-8/I? Date of introduction: 1968 (announced before December '67) Date of withdrawal: 1971. Total production run: 3698. Technology: DEC M-series logic modules, called M-series flip-chips as the term flip-chip was applied to the module format instead of to DEC's hybrid integrated circuits. M-series modules used TTL chips, with a +5 volt supply, packaged on the same board format used with the original flip-chips, but with double-sided card-edge connectors (36 contacts instead of 18). Modules were limited to typically 4 SSI ICs each. The M113, a typical M-series module, had 10 2-input nand gates and cost $23 in 1967 (the price fell to $18 in 1970). Wire-wrapped backplanes used 30-gauge wire. The PDP-8/I, as originally sold, supported the then-standard PDP-8 negibus. 4K words of core were packaged in a 1 inch thick module made of 5 rigidly connected 5 by 5 inch two-sided printed circuit boards. Connectors and support electronics occupied an additional 32 backplane slots. Nominally, the core memory (which, curiously, used a negative logic interface!) was supposed to run at a 1.5 microsecond cycle time, but many early PDP-8/I systems were delivered running at a slower rate because of memory quality problems. DEC went through many vendors in the search for good memory! The memory interface was asynchronous, allowing the CPU to delay for slow memory. DEC continued to make the classic PDP-8 until the problems with memory speed were solved. Reason for introduction: This machine was developed in response to the introduction of DIP component packaging of TTL integrated circuits. This allowed a machine of about the same performance as the original PDP-8 to fit in about half the volume and sell for a lower price. Reason for withdrawal: The PDP-8/E made slight performance improvements while undercutting the price of the PDP-8/I. Compatability: The core of the PDP-8 instruction set is present, and unlike the original PDP-8, IAC can be combined with rotate in a single microcoded Group 1 OPR instruction. Combined RAR and RAL or RTR and RTL produce the logical and of the expected results from each of the combined shifts. If the extended arithmetic element is present, the SWP (exchange AC and MQ) instruction works, but this was not documented. On large memory configurations, memory fetches from a nonexistant memory field take about 30 microseconds (waiting for a bus timeout) and then they return either 0000 or 7777 depending on the memory configuration and the field that was addressed. A front panel bug prevented continue after load-address without first clearing the machine. Standard configuration: CPU with 4K of memory, plus 110 baud current loop teletype interface. Pedestal, table-top and rack-mount versions were made. The pedestal mounted version was futuristic looking; the table-top version split the pedistal, with the CPU on the table and the power supply (the base of the pedistal) on the floor beside the table. The standard rack-mounted version had the power supply bolted to the right side of the rack while the CPU, mounted on slides, slid out of the left side of the rack. Expandability: 4K of memory could be added internally, and additional memory could be added externally using a rack-mounted MM8I memory expansion module for each 4K or 8K addition over 8K. The backplane of the PDP-8/I was prewired to hold a Calcomp plotter interface, with the adjacent backplane slot reserved for the cable connection to the plotter. There may be other built-in options. Initially, the CPU was sold with bus drivers for the PDP-8 negibus, allowing this machine to support all older DEC peripherals, but later machines were sold with posibus interfaces, and many older machines were converted in the field. A posibus to negibus converter, the DW08A, allowed use of all older PDP-8 peripherals, with small modifications. The change from negibus to posibus during the period of PDP-8/I production leads to confusion because surviving CPUs and peripherals may have any of three I/O bus configurations: Negibus, early posibus, or final posibus. The early posibus used the same connectors and cables as the negibus, with only 9 conductors per connector, while the final posibus used both sides of the connector paddles for 18 bus lines per connector. Y-shaped cables for converting from one physical bus layout to the other were available. To add to this confusion, some negibus PDP-8/I systems were rewired to use 18 conductor posibus cables with negative logic! Eventually, an add-on box was sold that allowed PDP-8/E (OMNIBUS) memory to be added to a PDP-8/I. Additionally, Fabritek sold a 24K memory box for the 8/I and PDP-12. Survival: Many PDP-8/I systems are in operating condition. ------------------------------ Subject: What is a PDP-8/L? Date of introduction: 1968 (announced before August '68) Date of withdrawal: 1971. Total production run: 3902. Price: $8,500 Technology: DEC M-series flip Chip modules, as in the PDP-8/I, with the same core memory as the 8/I, but with a memory cycle cycle of 1.6 microseconds to avoid the speed problems that plagued early -8/I systems. The positive I/O bus, or posibus, was a 100 ohm bus clamped between 0 and 3 volts with TTL drivers and receivers. This was packaged with 18 signal lines per 2-sided interconnect cable, using double-sided shielded mylar ribbon cable in most cases. Electrically, coaxial cable could be used, but the slots in the CPU box were too small for this. Reason for introduction: This machine was developed as a moderately successful exercise using M-series logic to produce a lower cost but moderately fast machine. The idea was to cut costs by limiting provisions for expansion. Reason for withdrawal: The PDP-8/E made performance improvements while slightly undercutting the price of the PDP-8/L. Compatability: The core of the PDP-8 instruction set is present, but all Group 3 OPR instructions are no-ops, even the Group 3 version of the CLA instruction. This is because there was no provision made for adding an EAE to this machine. Microcoding RAR and RAL together works as in the PDP-8/I. Finally, a new front panel feature was added, the protect switch. When thrown, this makes the last page of the last field of memory read-only (to protect your bootstrap code). The instruction to change the data field on an 8/L becomes a no-op when the destination data field is non-existant; on all other machines, attempts to address non-existant fields are possible. One option for expanding the 8/L was to add a box that allowed 8/E memory modules to be added to the 8/L; when this was done, access to nonexistant data fields becomes possible and always returns 0000 on read. Standard configuration: A CPU with 4K of memory, plus 110 baud current loop teletype interface was standard. Both rack-mount and table-top versions were sold (both 9" high by 19" wide by 21" deep). The backplane was on top, with modules plugged in from the bottom. The rack-mount version could be slid out for maintenance. Expandability: The CPU supported a new bus standard, the PDP-8 posibus. There is little space for in-box peripherals, but an expander box with the same volume as the CPU was available, the BA08A; this was prewired to hold an additional 4K of memory and to support in-box peripheral interfaces for such devices as a Calcomp plotter interface, a card-reader interface, a 4 line asynch terminal interface, a real-time clock, and more. DEC eventually offered the BM12L, an 8K expansion box that is essentially the same as the MM8I, but using positive logic and thus incompatable with the -8/I and -12. This allowed a total memory of 12K on a PDP-8/L. This contains precisely the modules needed to upgrade a 4K PDP-8/I or PDP-12 to an 8K machine, or to populate an MM8I box to add 8K of additional memory to an 8/I or PDP-12. Finally, DEC eventually offered a box allowing PDP-8/E (OMNIBUS) memory to be used with the PDP-8/L. PDP-8/L configurations with over 8K of memory were awkward because the front panel only showed one bit of the extended memory address. As a result, extra lights and switches for the additional bits of the memory address were mounted on the front of the memory expander boxes for the large configurations. A variety of posibus peripherals were introduced, most of which were built with the option of negibus interface logic (the -P and -N suffixes on these new peripherals indicated which was which). Many early PDP-8/L systems were sold with DW08A bus level converters to run old negibus peripherals. Posibus peripherals introduced after the PDP-8/L (and also used with posibus versions of the PDP-8/I) included: -- The TC08 DECtape controller (for 8 TU55 or 4 TU56). -- The DF32D fixed head disk controller (a posibus DF32). -- The FPP-12 floating point processor. -- The TR02 simple magnetic tape control. -- The RK08 disk subsystem, 4 disk packs, 831,488 words each. Survival: Many PDP-8/L systems are in operating condition. ------------------------------ Subject: What is a PDP-12? Date of introduction: 1969 (February or earlier). Date of withdrawal: 1973. Total production run: 3500? Price: $27,900 Technology: DEC M-series flip Chip modules, as in the PDP-8/I. Reason for introduction: This machine was developed as a follow-up to the LINC-8. Originally it was to be called the LINC-8/I, but somehow it got its own number. In effect, it was a PDP-8/I with added logic to allow it to execute the LINC instruction set. Reason for withdrawal: The LAB-8/E and the LAB-11 (a PDP-8/E and a PDP-11/20 with lab peripherals) eventually proved the equal of the PDP-12 in practice, and LINC compatability eventually proved to be of insufficient value to keep the machine alive in the marketplace. Compatability: This machine is fully compatable with the PDP-8/I, with additional instructions to flip from PDP-8 mode to LINC mode and back. IOT 0 could enable the API, causing trouble with later PDP-8 code that assumes IOT 0 is "Clear all flags". Also, the DECtape instruction DTLA (6766) becomes part of a stack-oriented extension to the instruction set, PUSHJ, on late model (or field updated) machines with the KF12-B backplane. The PDP-12 supported trapping of those LINC functions that were emulated by software on the LINC-8. This allowed it to run many LINC-8 bootable systems (but not all, due mostly incompatabilities in LINKtape support), and it allowed such things as emulation of LINKtape instructions for reading and writing disk. The TC12F Linktape controller could, with appropriate software, read or write DECtape. This support is unreliable, and is not software compatable with the TC01 or TC08 DECtape controller. Standard configuration: PDP-8/LINC CPU with 4K of memory, plus 110 baud current loop interface, plus output relay registers. In addition, the standard configuration included either two TU55 or one TU56 drive, with a PDP-12 only controller allowing it to handle LINCtape. In addition, a 12" scope was always included, with a connector that can connect to a second scope. Expandability: An analog to digital converter and multiplexor was needed to fully support knob-oriented LINC software. Other options included: -- the KW12 programmable lab clock. -- additional TU55 or TU56 drives (up to 8 transports). -- the BA12 expander box -- the PC05 paper tape reader punch (needs the BA12). Fabritek made a 24K memory box that could be added to a PDP-8/I or PDP-12. Survival: A few PDP-12 systems are in operating condition. ------------------------------ Subject: What is a PDP-8/E? Date of introduction: 1970 (during or before August). Date of withdrawal: 1978. Also known as: Industrial-8 (with a red color scheme) LAB-8/E (with a green color scheme) Price: $7,390 Technology: SSI and MSI TTL logic were used on these boards, and the entire CPU fit on 3 boards. Nominally, these were DEC M-series flip Chip modules, but in a new large format, quad-high (10.5 inch), extended-length (9 inch, including card-edge connector, excluding handles). The terms used for board height and length are based on the original working assumption that all flip-chips were plugged horizontally into a vertially mounted card-edge connector. On the PDP-8/E, the cards were plugged vertically down into a horizontally mounted connector, so many users incorrectly refer to these boards as quad-wide double-high. Interconnection between boards was through a new bus, the OMNIBUS. This eliminated the need for a wire-wrapped backplane, since all slots in the bus were wired identically. A new line of peripheral interfaces was produced, most being single cards that could be plugged directly into the inside the main enclosure. These included a set of posibus adapters allowing use of older peripherals on the new machine. Interboard connectors were needed for some multiboard options, including the CPU and memory subsystems. These used standard 36-pin backplane connectors on the opposite side of the board from the backplane. Some boards, notably memory boards, had a total of 8 connector fingers, 4 for the omnibus and 4 for interboard connectors. The core memory cycle time was 1.2 or 1.4 microseconds, depending on whether a read-modify-write cycle was involved (a jumper would slow all cycles to 1.4 microseconds). A 4K core plane was packaged on a single quad-wide double-high board, with most of the drive electronics packed onto two adjacent boards. Soon after the machine was introduced, an 8K core plane was released in the same format. Reason for introduction: The cost of the PDP-8/I and PDP-8/L was dominated by the cost of the interconnect wiring, and this cost was high as a result of the use of small circuit boards. By packing a larger number of chips per board, similar function could be attained in a smaller volume because less interboard communication was required. The PDP-8/E exploited this to achieve a new low in cost while attaining a new high in performance. Reason for withdrawal: This machine was slowly displaced by the PDP-8/A as the market for large PDP-8 configurations declined in the face of pressure from 16 bit mini and microcomputers. Compatability: As with the PDP-8/I and PDP-8/L, there are no limits on the combination of IAC and rotate instructions. Unlike the early machines, basic Group 3 OPR operations for loading and storing the MQ register work even if there is no extended arithmetic element. Finally, a new instruction was added, BSW; this swaps the left and right bytes in AC, and is encoded as a Group 1 OPR instruction using the "double the shift count bit". An odd quirk of this machine is that the RAL RAR combination ands the AC with the op-code, and the RTR RTL combination does an effective address computation loading the high 5 bits of AC with the current page and the lower bits of AC with the address field of the instruction itself! The EAE has a new mode, mode B. Previous EAE designs were single-mode. Mode B supports a large set of 24 bit operations and a somewhat more rational set of shift operations than the standard EAE. All prior EAE designs would hang on the microcoded CLA NMI (clear/normalize) instruction applied to a nonzero AC. This instruction is redefined to be a mode changing instruction on the 8/E. Standard configuration: A CPU with 4K of memory, plus 110 baud current loop teletype interface. Both a rack-mount table-top versions were sold (both 9" high by 19" wide by 21" deep). The rack mount version was mounted on slides for easy maintenance. The OMNIBUS backplane was on the bottom, with boards inserted from the top. The standard OMNIBUS backplane had 20 slots, with no fixed assignments, but the following conventional uses: -- KC8E programmer's console (lights and switches) -- M8300 \_ KK8E CPU registers -- M8310 / KK8E CPU control -- -- -- M833 - Timing board (system clock) -- M865 - KL8E console terminal interface. -- -- -- -- space for more peripherals -- -- -- M849 - shield to isolate memory from CPU -- G104 \ -- H220 > MM8E 4K memory -- G227 / -- -- -- space for more memory -- -- M8320 - KK8E Bus terminator Most of the early boards with 3 digit numbers were defective in one way or another, and the corrected boards added a trailing zero. Thus, the M833 was generally replaced with an M8330, and the M865 was replaced with the M8650. Expandability: The following are among the OMNIBUS boards that could be added internally: -- M8650 - KL8E RS232 or current loop serial interface. -- M8340 \_ Extended arithmetic element. -- M8341 / (must be attached in two slots adjacent to CPU. -- M8350 - KA8E posibus interface (excluding DMA transfers). -- M8360 - KD8E data break interface (one per DMA device). -- M837 - KM8E memory extension control (needed for over 4K). -- M840 - PC8E high speed paper tape reader-punch interface. -- M842 - XY8E X/Y plotter control. -- M843 - CR8E card reader interface. There were many other internal options. There was room in the basic box for another 20 slot backplane; taking into account the 2 slots occupied by the M935 bridge between the two backplanes, this allowed 38 slots, and a second box could be added to accomodate another 38 slot backplane, bridged to the first box by a pair of BC08H OMNIBUS extension cables. Given a M837 memory extension control, additional memory could be added in increments of 4K by adding G104, H220, G227 triplets. The suggested arrangement of boards on the OMNIBUS always maintained the M849 shield between memory other options. The one exception was that the M8350 KA8E and M8360 KD8E external posibus interfaces were typically placed at the end of the OMNIBUS right before the terminator. The following options were introduced later, and there were many options offered by third party suppliers. -- G111 \ -- H212 > MM8EJ 8K memory -- G233 / -- M8357 -- RX8E interface to RX01/02 8" diskette drives. -- M7104 \ -- M7105 > RK8E RK05 Disk Interface -- M7106 / -- M8321 \ -- M8322 \ TM8E Magtape control for 9 track tape. -- M8323 / -- M8327 / At one point, DEC packaged a PDP-8/E in a desk with no front panel controls other than power and bootstrap switch, along with an RX01 accessable from the front and a VT50 on top. This was sold as the Class-ic system, with an intended market in the classroom (hence the name); it was the forerunner, in terms of packaging, of many later DEC office products. Survival: It is still fairly common to find PDP-8/E systems on the surplus market, recently removed from service and in working condition or very close to it. A modest number are no-doubt still in service, and there is still a limited amount of commercial support from both DEC and third-party vendors. ------------------------------ Subject: What is a PDP-8/F? Date of introduction: 1972. Date of withdrawal: 1978. Technology: an OMNIBUS machine, as with the PDP-8/E. First use of a switching power supply in the PDP-8 family. Reason for introduction: The PDP-8/E had a large enough box and a large enough power supply to accomodate a large configuration. By shortening the box and putting in a small switching power supply, a lower cost OMNIBUS machine was possible. Reason for withdrawal: The PDP-8/A 800 displaced this machine, providing similar expansion capability at a lower cost. Compatability: The PDP-8/F used the PDP-8/E CPU and peripherals. Standard configuration: Identical to the PDP-8/E, except that the KC8E front panel was replaced with a KC8M front panel that had LEDs instead of incandescent lights; this front panel could also be installed on PDP-8/E systems, but the PDP-8/E front panel could not be used on a PDP-8/F because of the lack of a +8 supply for the lights. The original PDP-8/F box had a defective power supply, but a revised (slightly larger) box corrected this problem. Expandability: This machine could be expanded using all PDP-8/E OMNIBUS peripherals, including the external expansion chassis. The relatively small internal power supply and the lack of room for a 20 slot bus expander inside the first box were the only limitations. There were minor compatability problems with some options, for example, the power-fail auto-restart card, as originally sold, was incompatable with the PDP-8/F power supply. Survival: As with the PDP-8/E, these machines are moderately common on the surplus market, and frequently in working condition. ------------------------------ Subject: What is a PDP-8/M? Date of introduction: 1972. Date of withdrawal: 1978. Technology: This machine was a PDP-8/F (with a PDP-8/E CPU) Reason for introduction: DEC knew that OEM customers were an important market, so they packaged the PDP-8/F for this market, with no hardware changes behind the front panel. Reason for withdrawal: Same as the PDP-8/F Compatability: The PDP-8/M used the PDP-8/E CPU and peripherals. Standard configuration: Identical to the PDP-8/F, except that the KC8M front panel was replaced with a minimal function panel and the color scheme was different. Because of this, one of the following options were required: -- M848 -- KP8E Power fail and auto-restart. -- M847 -- MI8E Hardware Bootstrap Loader. Expandability: All options applying to the PDP-8/F applied. In addition, the KC8M front panel (standard with the PDP-8/F) was available as an option. Survival: As with the PDP-8/F. ------------------------------ Subject: What is a PDP-8/A? Date of introduction: 1975 Date of withdrawal: 1984 Also known as: DECdatasystem 310 (an 8/A 500 sold as a word-processor) Technology: This machine used the OMNIBUS with a new single-board CPU. The backplane was reoriented so that boards plugged into it from the front, with the board held horizontally. Reason for introduction: Using TTL MSI and LSI components, DEC was able to reduce the PDP-8 CPU to a single oversize board (formally, hex height, double width). Similarly, they were able to make an 4K core memory board, and later, an 8K board in this format, and they were able to introduce a static RAM card using semiconductor memory. The minimum system was reduced to 3 boards. The market for the PDP-8 was dominated by small systems, with fewer and fewer customers needing large-scale expandability. Thus, the 20 slot backplane of the early Omnibus machines was too big; with the new single board CPU and memory, a 12 slot backplane was enough, allowing further cost reductions. Reason for withdrawal: The market for the PDP-8 family was shrinking in the face of pressure from larger minicomputers and the new monolithic microcomputers. After 1975, many PDP-8 sales were to captive customers who had sufficient software investments that they could not afford to move. Only the word-processing and small business markets remained strong for first-time PDP-8 sales, and in these, the specialized DEC VT-78 and DECmate machines were more cost effective than the open architecture OMNIBUS machines. Compatability: The new PDP-8/A CPU was largely compatable with the PDP-8/E CPU, except that the combination of RTR and RTL (Group 1 OPR instructions) loaded the next address. The power-fail auto-restart option included the standard skip on power low instruction, but also a new skip on battery empty instruction to test the battery used for back-up power on the new solid state memory. The standard parallel port on the M8316 port was not software compatable with the earlier line-printer interfaces used with device code 66. Standard configuration: The PDP-8/A was sold with a new short OMNIBUS backplane, mounted on its side above a power supply and a battery to back up the solid state memory. The minimum configuration included a limited function control panel and the following components on the bus: -- M8315 -- KK8A CPU board -- M???? -- MS8A 1K to 4K solid state memory. -- M???? -- MR8A ROM companion for the MS8A. -- M8316 -- DKC8AA serial/parallel interface and clock. The M8316 board contained a remarkable but useful hodgepodge of commonly used peripherals, including the console terminal interface, a parallel port, the power/fail auto-restart logic, and a 100 Hz real time clock. The original configuration sold had a 10 slot backplane and a poor power supply. The later base model had a 12 slot backplane, the 8/A 400. Expandability: All PDP-8/E peripherals and options could be used with the PDP-8/A. The KK8A cpu was not as fast as the KK8E used in the PDP-8/E, but the KK8E CPU could be substituted for the KK8A CPU, and many PDP-8/A systems were sold with this substitution. A box with a 20 slot backplane, the 8/A 600, was available for large configurations. A pair of PDP-8/A backplanes could be connected using BC08H cables, and there was a special cable, the BC80C, for connecting a hex wide 8A backplane to a PDP-8/E, -8/F or -8/M backplane. By late 1975, the PDP-8/A was being sold in a workstation configuration, with the CPU and dual 8" diskette drives in a desk with a video terminal (VT52) and letter quality printer on top. This followed the pattern set by the Class-ic packaging of the PDP-8/E, but it was aimed at the word-processing market. The following additional PDP-8/A (hex) boards were offered: -- G649 \_ MM8AA 8K Core stack (too slow for 8/E CPU!). -- H219A / MM8AA 8K Core memory control. -- G650 \_ MM8AB 16K Core stack (ok for 8/E CPU!). -- H219B / MM8AB 16K Core memory control. -- M???? -- MR8F 1K ROM (overlayable with core). -- M8317 -- KM8A memory extender (with variations). -- M8319 -- KL8A 4 channel RS232 or current loop serial I/O. -- M8433 -- RL8A controller for 1 to 4 RL01/RL02 disk drives. -- M???? -- FPP8A floating point processor. The PDP-8/A model 800 was the same as the model 600, but with the FPP8A floating point processor included as part of the package. -- M8416 -- KT8AA Memory management unit for up to 128K. -- -- KC8AA Programmer's Console (requires M8316) -- M8417 -- MSC8DJ 128K DRAM MOS Memory. Note that memory extension to 128K was a new PDP-8/A feature that was necessarily incompatable with the older PDP-8 memory expansion options, although the conventional PDP-8 memory expansion instructions still operate correctly on the first 32K. Access to additional fields involved borrowing IOT instructions that were previously dedicated to other devices. The MM8A options require the use of a box with a -20V power supply. Also, the use of the MSC8 DRAM memory cards requires a CPU that supports the memory stall signal, early PDP-8/E CPUs did not. Survival: As with the PDP-8/E, these machines are moderately common on the surplus market and a modest number are still in use. Because the original machines were less expensive than and slower than 8/E, they are more likely to be simply discarded instead of sold as surplus. ------------------------------ Subject: What is a VT78? Date of introduction: 1978 Date of withdrawal: 1980 (Displaced by the DECmate) Also known as: DECstation 78 Technology: Based on the Intersil/Harris 6100 microprocessor, packaged in a VT52 case. The 6100 processor was able to run at 4 MHz, but in the VT78, it was only clocked at 2.2 MHz because of the speed of the DRAM used and the deliberate use of graded out chips. Reason for introduction: Using TTL MSI and LSI components, DEC could pack a system into vacant space in a standard terminal case, allowing PDP-8 systems to compete with personal computers in the small business and office automation market. This was a natural follow-on to the desk-mounted workstation configurations in which the PDP-8/A was already being sold. Compatability: The Group I OPR combinations RAL RAR and RTL RTR are no-ops. Unlike all earlier PDP-8 models, autoindex locations 10 to 17 (octal) only work in page zero mode; these operate like all other memory locations when addressed in current page mode from code running on page zero. Other than this, it is fully PDP-8/E compatable, even at the level of I/O instructions for the standard periperals; this was the last PDP-8 to offer this level of compatability. It was not possible to continue from a halt without restarting the machine. In addition, none of the peripherals available on this machine needed DMA (data break) transfers. Standard configuration: The VT78 was sold with 16k words of DRAM with the keyboard and display of the VT52 terminal. An RX01 dual 8" diskette drive was standard, packaged in the pedestal under the terminal. The console (device 03/04) and the serial ports (devices 30/31 and 32/33) are compatible with the M8650 KL8E, with the latter extended to allow software controlled baud rate selection. There are two parallel ports; device 66 (compatible with the M8365 printer controller) and device 47, compatible with the nonstandard port on the M8316 DKC8AA. There is also a 100Hz clock compatible with the clock on the M8316 DKC8AA. The standard ROM boots the system from the RX01 after setting the baud rates to match that selected by the switches on the bottom of the VT52 case. Expandability: This was a closed system, with few options. The base configuration was able to support two RX01 drives (later RX02), for a total of 4 transports. Various boot ROM's were available, including a paper-tape RIM loader ROM for loading diagnostics from tape. Another ROM boots the system from a PDP-11 server in the client/server configuration used by WPS-11. Survival: There are probably many VT78 systems still in use. ------------------------------ Subject: What is a DECmate I? Date of introduction: 1980 Date of withdrawal: 1984 (Phased out in favor of the DECmate II) Also known as: DECmate (prior to the DECmate II, no suffix was used) VT278 Technology: Based on the Intersil/Harris 6120 microprocessor, packaged in a VT-100 box with keyboard and display. Reason for introduction: This machine was aimed primarily at the market originally opened by the VT78, using the IM6120 as a substitute for the older 6100 chip and optimizing for minimum cost and mass production efficiency. Compatability: A new feature was introduced in the 6120 microprocessor: The Group I OPR combination RAL RAR was defined as R3L, or rotate accumulator 3 places left, so that byte swap (BSW) is equivalent to R3L;R3L. RTR RTL remained a no-op, as in the 6100. Also, the EAE operations not implemented in the basic CPU cause the CPU to hang awaiting completion of the operation by a coprocessor. Unfortunately, no EAE coprocessor was ever offered. The printer port offered software baud-rate selection compatable with the VT78 baud-rate selection scheme. The dual-port data communications option was flexible but completely incompatable with all previous PDP-8 serial ports. The console and printer ports are not fully compatable with the earlier PDP-8 serial ports. Specifically, on earlier serial interfaces, it was possible to test flags without resetting them, but on the DECmate machines, testing the keyboard input flag always resets the flag as a side effect. In addition, on the console port, every successful test of the flag must be followed by reading a character or the flag will never be set again. It was not possible to continue from a halt without restarting the machine. The large amount of device emulation performed by the CPU in supporting screen updates severely limits the ability of the system to run in real time. Standard configuration: The DECmate I was sold with 32k words of memory, with a small control memory added to handle control/status, console device emulation and boot options. The console terminal keyboard and display functions are largely supported by code running in control memory (a less expensive alternative to dedicating hardware for this, as was done in the VT78). The DECmate I came with an integral printer port, compatable with the VT78 (device 32/33), and it had an RX02 dual 8 inch diskette drive, mounted in the short pedistal under the terminal/CPU box. A 100Hz clock was included, as in the VT78 and PDP-8/A. Expandability: This was a closed system, with limited options. Specifically, a second RX02 could be connected (or an RX01, because that had a compatable connector), the DP278A and DP278B communications boards (really the same board, but the DP278B had 2 extra chips), and the RL-278 disk controller, able to accomodate from 1 to 4 RL02 rack mount disk drives. When the DP278A option is added, additional routines in control memory come alive to handle terminal emulaton and allow diskless operation. The terminal emulator is an extended VT100 subset that is essentially compatable in 80 column mode. The DP278A option could support both asynchronous and synchronous protocols, and the DP278B could handle SDLC and other nasty bit-stuffing protocols. Various pedestal and desk configurations were sold for housing the RX01 and RX02 drives, most being teacart style designs, but there was also a pedestal version that was essentially a repackaging of the RX02 with either 2 or 4 new 8 inch disk transports (physically incompatable with earlier DEC transports). Survival: Many DECmates are still in use, and they are fairly common on the surplus market. They are found in small numbers just about anywhere large numbers of early PC vintage machines are found. ------------------------------ Subject: What is a DECmate II? Date of introduction: 1982 Date of withdrawal: 1986 Price: $1,435 Technology: Based on the 6120 microprocessor, this shared the same packaging as DEC's other competitors in the PC market, the Rainbow (8088 based) and the PRO-325 (PDP-11 based). Reason for introduction: This machine was introduced in order to allow more flexibility than the DECmate I and to allow more sharing of parts with the VT220 and DEC's other personal computers. Compatability: Same as the DECmate I, except it could continue from a halt. There was better hardware for device emulation support, allowing for somewhat better real-time performance. The data communications port was an incompatable improvement on the incompatable DECmate I communications port. No built-in terminal emulation was provided, and the data communications port supported only one line, but aside from this, the data communications port is essentially as powerful as the DP-278B on the DECmate I. Standard Configuration: The DECmate II was sold with 32K of program memory, plus a second full bank for dedicated control panel function emulation. Code running in the second bank is sometimes referred to as slushware; it looks like hardware to the PDP-8 user, but it is actually device emulation software that is loaded from the boot diskette. An integral RX50 dual 5 1/4 inch diskette drive with an 8051 controller chip was included, along with a printer port, a 100Hz real-time clock, single data communications port, and interfaces to the monitor and keyboard. The diskette drive can read single-sided 48 track-per-inch diskettes, so it might be possible to read (but not write) IBM PC diskettes on it. Expandability: This was the most open of the DECmate systems, with a number of disk options: An additional pair of RX50 drives could be added, and with the RX78 board, it could support a pair of dual 8 inch drives, either RX01 or RX02. As an alternative to the RX78, there was a controller for an MFM hard drive. The interface to the RX78 board wasn't fully compatable with earlier interfaces to RX01 and RX02, and there was no way to have both an RX78 and an MFM drive. The MFM drive could be up to 64 MB, with 16 sectors per track, 512 bytes each and at most 8 heads and 1024 (or possibly 4096) cylinders. A power supply upgrade was needed to support the MFM drive. DEC sold this machine with 5, 10 and 20 meg hard drives, Seagate ST-506, 412, and 225 respectively. A graphics board supporting a color monitor could be added in addition to the monochrome console display; two variants of this board were produced during the production run, all slightly incompatable. A coprocessor board could be added, with communication to and from the coprocessor through device 14. DEC sold three boards, an APU board (Z80 and 64K), and two XPU boards (Z80, 8086 and either 256K or 512K). If these added processors are used, the 6120 processor is usually used as an I/O server for whatever ran on the coprocessor. The XPU boards used a Z80 for I/O support, so 8086 I/O was very indirect, particularly if it involved I/O to a PDP-8 device that was emulated from control memory. Despite this, the DECmate version of MS/DOS is generally faster than MS/DOS on more recent 80286 and 80386 based IBM PCs because of effective use of the coprocessors (but they couldn't run MS/DOS code that bypasses MS/DOS for I/O). Survival: As with the DECmate I. ------------------------------ Subject: What is a DECmate III? Date of introduction: 1984 Date of withdrawal: 1990 Price: $2,695 Technology: Same as the DECmate II. Reason for introduction: Again, DEC discovered that the market for large systems was dominated by other products, and that the PDP-8 based products were rarely expanded to their full potential. Thus, there was no point in paying the price for expandability. Compatability: Same as the DECmate II, except that the printer port is fixed at 4800 baud. Standard Configuration: The DECmate III was sold with 32K of program memory, plus a second full bank for dedicated control panel functions, an integral RX50 dual 5 1/4 inch diskette drive with an 8051 controller chip, a printer port, a 100Hz real-time-clock, a data communications port, and interfaces for the VR-201 monitor and keyboard. Expandability: A revised version of the Z80 based coprocessor for the DECmate II was available, and a graphics board largely compatable with the later DECmate II graphics board could be added allowing the standard monochrome monitor to be replaced with a VR-241 color monitor. Two monitor configurations were not supported. An obscure variant of the DEC scholar modem was also supported as an option. Survival: As with the DECmate I. ------------------------------ Subject: What is a DECmate III+? Date of introduction: 1985 Date of withdrawal: 1990 Technology: Same as the DECmate II. Reason for introduction: This machine apparently represents the last gasp of the PDP-8, hunting for the remains of the ever-shrinking market niche that the earlier DECmates had carved out. The market niche was not there, and the production runs for this machine were short enough that UV erasable EPROM technology was used where earlier DECmates had used mask programmed chips. Compatability: Same as the DECmate II, but the machine was unable to read 48 track per inch IBM formatted diskettes. Again the printer port was fixed at 4800 baud. Standard Configuration: The DECmate III+ was sold with 32K of program memory, plus a second bank for dedicated control panel functions, an integral RX33 single 5 1/4 inch diskette drive with an 8751 controller chip, a printer port, a data communications port and interfaces to the monitor and keyboard. A hard disk controller compatable with the optional one on the DECmate II was included, supporting an integral ST-225 20 MB disk; it is likely that it can only handle up to 1024 cylinders, but it is otherwise compatable with the DECmate II. Expandability: The same coprocessor option sold with the DECmate III was available, but because of the difficulty of adding a second floppy drive, this was rarely used (the Z80 was most likely to be used to run CP/M, but that system requires two drives to handle the installation procedure; an appropriately configured bootable image created on a DECmate II or III could run on a DECmate III+). The same graphics board as used on the DECmate III was also available. The circuit traces and connectors for the Scholar modem are present, but this option was never sold on the DECmate III+. Survival: As with the other DECmates. ------------------------------ End of PDP-8 Summary of Models and Options (posted every other month) ********************************************************************* Article 1117 of alt.sys.pdp8: Newsgroups: alt.sys.pdp8 Path: bigblue.oit.unc.edu!concert!news-server.ncren.net!taco.cc.ncsu.edu!lll-winken.llnl.gov!uwm.edu!math.ohio-state.edu!howland.reston.ans.net!Germany.EU.net!news.dfn.de!news.rwth-aachen.de!urmel.informatik.rwth-aachen.de!newsserver.rrzn.uni-hannover.de!news From: bb@informatik.uni-hannover.de (Bernhard Baehr) Subject: Macintosh PDP-8/E Simulator Message-ID: <1994Dec9.162550.22248@newsserver.rrzn.uni-hannover.de> Sender: news@newsserver.rrzn.uni-hannover.de (News Service) Reply-To: bb@informatik.uni-hannover.de Organization: RRZN Date: Fri, 9 Dec 1994 16:25:50 GMT Lines: 40 I announce the availability of the beta version of my simulator for the DEC PDP-8/E minicomputer running on the Apple Macintosh computer. The simulated machine is a PDP-8/E with 4K words of memory and a ASR 33 console teletype. Optionally a MC8-E Memory Extension (with up to 32K words of memory), an EAE, an auxiliary ASR 33 teletype, a high speed paper tape reader and punch, a RK8-E disk system, a LP8-E line printer and a Real Time Clock can be attached to the simulated PDP-8/E. The simulator is based on the PDP-8/E emulator of Bill Haygood. It is known to run on a wide variety of Macintosh computers from the SE/30 to the Power Macintosh running System 6.0.4 to 7.5. (Probably it runs on any Macintosh with System 4.1 or better and 128K ROMs.) On the fastest 68040 Macintoshs the simulated PDP-8/E runs nearly with the speed of a hardware PDP-8/E. The simulator provides a comfortable user interface for running, writing and debugging PDP-8 software. For each device, there is a separate window which displays the internal state of the device (e. g. register and - disassembled - memory content). Register and memory content can be modified by mouse clicking. Other features of the simulator are breakpoints, break opcodes, single step execution, a trace mode for the PDP-8/E and much more. The simulated ASR 33 teletypes provide all comfort of Macintosh text editor windows. There is no manual for the PDP-8/E Simulator, but the program has full Balloon Help support, and there is a help window which gives detailed information about the PDP-8 instruction set implemented by the simulator and hints for operating the simulator. Anybody who wants to use and test the simulator, which, although it is version 1.0 beta, has reached a very stable state, may ask me to send him a copy of the program by E-mail. Bernhard Baehr bb@informatik.uni-hannover.de Article 1118 of alt.sys.pdp8: Newsgroups: alt.sys.pdp8 Path: bigblue.oit.unc.edu!concert!news-server.ncren.net!taco.cc.ncsu.edu!lll-winken.llnl.gov!uwm.edu!math.ohio-state.edu!howland.reston.ans.net!agate!darkstar.UCSC.EDU!news.hal.COM!decwrl!netcomsv!netcom.com!edmoran From: edmoran@netcom.com (Ed Moran) Subject: Historical clubs, newsletters? Message-ID: Organization: NETCOM On-line Communication Services (408 261-4700 guest) X-Newsreader: TIN [version 1.2 PL1] Date: Sat, 10 Dec 1994 17:14:22 GMT Lines: 24 Hi, all! I'm getting used to my internet account now. I was wondering.. Are there any organizations around for old computer buffs? Informal clubs and newsletters? I've discovered the IEEE's Annals of computer history, and found a fair number of books on the subject (thank you, Mr Cortada, wherever you are..) But I'm looking for a way to find old machines (I have a garage now, too ..=]), and hopefully have a shoulder to cry on when I try to get it running. As for myself, I worked a couple of summers at the old Byte Shop on Bascom, San Jose, building Imsais and fixing Altairs, and always had a passing interest in restoring a PDP-11, a Nova or the like. Now that I have the resources, I'm beginning the search. Any ideas? Where do mainframes go whenthey die? Thanks! - Ed -- Ed Moran, edmoran@netcom.com The above opinions are unsuitable for re-use, PO Box 72OO72 San Jose, Calif. Please dispose of properly. Article 1119 of alt.sys.pdp8: Path: bigblue.oit.unc.edu!concert!news-feed-1.peachnet.edu!gatech!howland.reston.ans.net!news.sprintlink.net!bga.com!hsnewman From: hsnewman@bga.com (Harris Newman) Newsgroups: alt.sys.pdp8 Subject: PDP-10 Emulator wanted Date: 10 Dec 1994 00:05:54 GMT Organization: Real/Time Communications - Bob Gustwick and Associates Lines: 8 Message-ID: <3card2$mk6@giga.bga.com> NNTP-Posting-Host: ivy.bga.com X-Newsreader: TIN [version 1.2 PL2] Sorry bout the misspost, but yall may know of a pdp-10 emulator out there. -- Remember: Zero is always better than nothing! hsnewman@bga.com Article 1120 of alt.sys.pdp8: Path: bigblue.oit.unc.edu!concert!news-server.ncren.net!taco.cc.ncsu.edu!lll-winken.llnl.gov!koriel!cs.utexas.edu!howland.reston.ans.net!math.ohio-state.edu!hobbes.physics.uiowa.edu!news.uiowa.edu!news From: jones@pyrite.cs.uiowa.edu (Douglas W. Jones,201H MLH,3193350740,3193382879) Newsgroups: alt.sys.pdp8 Subject: Re: Historical clubs, newsletters? Date: 12 Dec 1994 17:11:52 GMT Organization: University of Iowa, Iowa City, IA, USA Lines: 66 Distribution: world Message-ID: <3ci08o$sl3@nexus.uiowa.edu> References: NNTP-Posting-Host: pyrite.cs.uiowa.edu From article , by edmoran@netcom.com (Ed Moran): > > I was wondering.. Are there any organizations around for old computer > buffs? > > Ed Moran, edmoran@netcom.com > PO Box 72OO72 San Jose, Calif. You want to get in touch with the Computer History Association of California. Here are some snips from the most recent edition of their newsletter: ------------------------------------------------- The ANALYTICAL ENGINE Newsletter of the Computer History Association of California ISSN 1071-6351 Volume 2, Number 2, October 1994 Kip Crosby, Managing Editor Jude Thilman, Telecommunications Editor ------------------------------------------------- Computer History Association of California 3375 Alma Street Apt. 263 Palo Alto, CA 94306-3518 ------------------------------------------------- ADDRESSES OF CORRESPONDING ORGANIZATIONS ------------------------------------------------- Charles Babbage Institute, 103 Walter Library, 117 Pleasant Street SE, Minneapolis, MN 55455. Judy E. O'Neill, associate director. The Computer Museum, 300 Congress Street, Boston MA 02210. Brian C. Wallace, curator of historical computing. Historical Computer Society, 10928 Ted Williams Place, El Paso TX 79934. CompuServe 100116,217. David A. Greelish, director and editor. ------ this address is out of date -------- International Association of Calculator Collectors, 10445 Victoria Avenue, Riverside CA 92503. Guy Ball, Bruce L. Flamm, directors. International Interactive Communications Society, 2601 Mariposa Street, San Francisco CA 94110. Sheila Farrell, membership secretary. Lambda Software Publishing, 149 West Hilliard Lane, Eugene OR 97404. David A. J. McGlone, editor and publisher. _The Mathematical Intelligencer_, Springer-Verlag New York, 175 Fifth Avenue, New York, NY 10010. Chandler Davis, editor-in- chief. Unusual Systems, 220 Samuel Street, Kitchener, Ontario N2H 1R6, Canada. Kevin Stumpf, president. Hope all that helps! Doug Jones jones@cs.uiowa.edu Article 1121 of alt.sys.pdp8: Path: bigblue.oit.unc.edu!concert!rutgers!uwm.edu!vixen.cso.uiuc.edu!howland.reston.ans.net!pipex!sunic!trane.uninett.no!ifi.uio.no!wabbit.cc.uow.edu.au!metro!inferno.mpx.com.au!dialup-17.mpx.com.au!user From: George.Bray@mpx.com.au (George Bray) Newsgroups: decus.nop,aus.general,aus.comms,alt.sys.pdp8,alt.sys.pdp11,biz.dec Subject: Re: Aust. COMPUTER MUSEUM Society now Official. Date: Thu, 22 Dec 1994 23:55:49 +1000 Organization: Sand Consulting Pty Ltd Lines: 16 Message-ID: References: <1994Dec21.223501.15131@decus.org.au> NNTP-Posting-Host: dialup-17.mpx.com.au Xref: bigblue.oit.unc.edu alt.sys.pdp8:1121 biz.dec:654 > > Current membership fees are $25.oo for individuals > $10.oo for students/pensioners > > Membership forms are available from the Secretary or Treasurer. Are the forms on the web? > > > v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v > John Geremin, Treasurer, Australian COMPUTER MUSEUM Society Inc. > -^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^- George Bray Article 1122 of alt.sys.pdp8: Newsgroups: alt.sys.pdp8 Path: bigblue.oit.unc.edu!concert!rutgers!rochester!udel!news.mathworks.com!news2.near.net!howland.reston.ans.net!pipex!lyra.csx.cam.ac.uk!warwick!uknet!cix.compulink.co.uk!usenet From: oddjob@cix.compulink.co.uk ("Stephen Walters") Subject: Re: Historical clubs, newsletters? Message-ID: Organization: Skills Unlimited References: <3ci08o$sl3@nexus.uiowa.edu> Date: Wed, 21 Dec 1994 21:54:18 GMT X-News-Software: Ameol Lines: 19 Well in London, there is the CLASSIC COMPUTER CLUB Setup, by ME, to help people who are interested in collecting old computers. My oldest machine is my 12kword PDP 8e with duff asr33, Intersil Intercept, and very shortly a Valve Analog Computer (age unknown and VERY big). My tel no is +44 0956-544202 Mercury 1-2-1 mobile and I have e-mail and on occasion FAX, too. The club has been running for ? five years and is quite small group. Every time we get publicity the is a barrage of e-mails, snail-mail 'phone calls etc. I just thought I'd mention it. oddjob@cix.compulink.co.uk Article 1123 of alt.sys.pdp8: Path: bigblue.oit.unc.edu!concert!news.duke.edu!convex!cs.utexas.edu!howland.reston.ans.net!quagga.ru.ac.za!munnari.oz.au!news.unimelb.EDU.AU!ucsvc.ucs.unimelb.edu.au!decus!geremin Newsgroups: decus.nop,aus.general,aus.comms,alt.sys.pdp8,alt.sys.pdp11,biz.dec Subject: Aust. COMPUTER MUSEUM Society now Official. Message-ID: <1994Dec21.223501.15131@decus.org.au> From: geremin@decus.org.au Date: 21 Dec 94 22:35:01 AEST Organization: DECUS Australia Lines: 57 Xref: bigblue.oit.unc.edu alt.sys.pdp8:1123 biz.dec:655 AUSTRALIAN COMPUTER MUSEUM SOCIETY NOW INCORPORATED in NEW SOUTH WALES. The Australian Computer Museum Society is now incorporated as from the 16th December, 1994 under the Associations Incorporation Act 1984 (in NSW). The President is Graeme PHILIPSON, phone 02-286 5900, fax 02-267 2094, e-mail IN%"graemep@spg.mhs.compuserve.com" The Secretary is Michael CHEVALLIER, phone 02-498 3383, e-mail IN%"chevallier@decus.org.au" The Treasurer is John GEREMIN, phone 02-764 4855, fax 02-764 4679, e-mail IN%"geremin@decus.org.au" The society's ADDRESS is Australian COMPUTER MUSEUM Society Inc. c/- P.O. Box 103, Killara, NSW, 2071. Australia. ____________________________________________________ The Society is seeking BUSINESS SPONSORSHIPS from Computer Businesses to help pay the rent on its storage space at Homebush. In the new year the society will be looking for VENDOR SPONSORSHIPS from Computer Manufacturers to employ part-time curators. The Society also needs COMMERCIAL SPONSORS and DONATIONS from any interested business to help us establish our offices and to institute our special projects. ____________________________________________________ Current membership fees are $25.oo for individuals $10.oo for students/pensioners Membership forms are available from the Secretary or Treasurer. v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v John Geremin, Treasurer, Australian COMPUTER MUSEUM Society Inc. -^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^- Article 1124 of alt.sys.pdp8: Path: bigblue.oit.unc.edu!concert!hearst.acc.Virginia.EDU!caen!msunews!harbinger.cc.monash.edu.au!decus!geremin From: geremin@decus.org.au Newsgroups: decus.nop,aus.general,aus.comms,alt.sys.pdp8,alt.sys.pdp11,biz.dec Subject: Re: Aust. COMPUTER MUSEUM Society * Mship Form. Message-ID: <1994Dec23.231447.15134@decus.org.au> Date: 23 Dec 94 23:14:46 AEST References: <1994Dec21.223501.15131@decus.org.au> Organization: DECUS Australia Lines: 91 Xref: bigblue.oit.unc.edu alt.sys.pdp8:1124 biz.dec:656 In article , George.Bray@mpx.com.au (George Bray) writes: >> >> Current membership fees are $25.oo for individuals >> $10.oo for students/pensioners >> >> Membership forms are available from the Secretary or Treasurer. > > > Are the forms on the web? Not really - but one is appended here. >> >> >> v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v >> John Geremin, Treasurer, Australian COMPUTER MUSEUM Society Inc. >> -^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^- > > George Bray -- Regards, John G. (alias 'megaJOHN') v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v-v John Geremin, Treasurer, Australian COMPUTER MUSEUM Society Inc. IN%"geremin@decus.org.au" or fax: 02- 764 4679 (24 hours). -^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^-^- ------- Application for Membership of Society. Australian COMPUTER MUSEUM Society Inc. ======================================= I, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (full name of applicant) of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (residential address) . . . . . . . . . . . . . . . . . . . . hereby apply to become a member (occupation) of the Australian Computer Museum Society Inc. In the event of my admission as a member, I agree to be bound by the rules of the society for the time being in force. . . . . . . . . . . . . . . . . . . . . . . . . Date . . / . . . / . . Signature of applicant Phone (Home). . .- . . . . . . . E-mail . . . . . . . . . . . . . . . . . Phone (Bus.). . .- . . . . . . . Fax . . . . . . . Mobile . . . . . . . . Postal Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Membership Fees $ 25.oo per annum. [$10.oo pensioner/student] Business Sponsorships are welcome, please call the Treasurer, 02-764 4855. return form, cheque to: A.C.M.S.Inc. p.o. box 103, KILLARA. NSW 2071. ------------ ------------- -------------------- A. C. M. S. Initial Member Survey. Please tick below your special interests in A.C.M.S. project activities, a) . . . Computer Hardware - collection and restoration. b) . . . Software Archive and Media Repository. c) . . . Oral History - Interviews and followups. d) . . . Library of Manuals and other printed documentation. e) . . . Database of Technical - Personal - General Information. f) . . . Committee assistance - general organisation. g) other special interests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . h) personal collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ----------