2 Feb
2008
2 Feb
'08
10:39 a.m.
Roger Ivie said the following on 2/2/2008 1:16 PM:
I did a small amount of work with ISIS, but after I had used CP/M. I
used an Intel PDS development system for the 8051 to debug some
firmware; I think it was for DEC's SCSI floppy controller.
The PDS was interesting in that it was a portable system about the size
of a Kaypro and had *two* 8085s. ISIS gave you an A> or B> prompt, but
it indicated to which processor you were speaking rather than which
drive was the default.
Now *that* was multiprocessing! I remember it well. In fact I still
have a working one. With ISIS-PDS there was a logical locking so that
you could have both processors (actually *two* complete computers, each
with its own 64KB of RAM) doing disk i/o concurrently and they wouldn't
scramble each other's files.
It came with a single full-height floppy drive. I changed mine to have
two half-height ones and if I was careful I could run ISIS-PDS on one of
the processors and CP/M-80 or CP/M Plus on the other. ISIS-PDS would
boot from the internal bubble memory (128KB) and CP/M would boot from
the floppy. I would do my Intel development work on the ISIS side and
document it in Wordstar on the CP/M side as I was developing. it.
There was no mechanism to keep one side from clobbering the other side's
files on floppies, so I had to keep that straight in my head. At the
time it was not hard to do, but today I am probably too lazy to keep it
all straight. ;)
Dave