PDP-8 Dual Process System
| 8-77
|
Richard M. Merrill, Digital Equipment Corporation, Maynard,
Massachusetts
The purpose of this system is to expedite the programming of
multiprocessing problems on the PDP-8 and PDP-8/S. It
maximizes both the input speed and the portion of real time
actually used for calculations by allowing the program to run
during the intervals between issuing I/O commands dnd the
raising of the device flag to signal completion of the com
mand. The technique also allows queuing of input data or
commands so that the user need not wait while his last line
is being processed, and so that each line of input may be
processed as fast as possible regardless of its length. The
system uses the interrupt facilities and has less than 3%
overhead on the PDP-8/S (about 0.1% on the PDP-8).
This method is especially useful for a slower machine where
the problem may easily be calculation limited but would,
without such a system, become I/O bound.
The program may also be easily extended to handle input
from an A/D converter. Here, the input would be buffered
by groups of readings terminated either arbitarily in groups
of N or by zero crossings.
This program can increase the I/O to computation efficiency
of some programs by 100%. It can do this even for single
Teletype. Each user will probably want to tailor the program
to his individual needs.
| Storage Requirement: | 6008 registers for two TTY's plus buffer
space. (Several device configurations
are possible.)
|
| Catalog:
| November 1969
|