Date : Wed, 08 Sep 1982 1828-:00PDT
From : Jeffrey@Office-2
Subject: S100 SBC Print Despooler
For me, one of the annoying things about my CP/M is its inability to
print while I do other things. I've tried despool with poor
results. I much rather have a true multi-programmed system such as
Unix or concurrent CP/M, etc.
But - by now I've have a substantial investment in not changing. Its
not so much the price of the software or hardware; its more the time
I've spent tailoring programs, command files, procedure, etc. to do
things just the way I like.
I'm therefore interested in a print spooling mechanism which I can
add to my Godbout 8085/88 S100 system.
The easiest solution seemed to involve the acquisition ($150 or so)
of a 16k buffer to fit inside my Epson MX80.
Well, that seemed simple. When installed in my printer, the buffer
didn't work. It worked at the shop however. After wasting a good
deal of time, I came to learn that my Godbout interfacer II parallel
port is not really what an Epson want to see. I've just been lucky
that it drives the printer at normal speed (i.e. printer speed).
Addition of the buffer increased the data transfer rates so much that
data would no longer transfer. End of buffer idea. Of course I soon
thereafter bought Godbout's Interfacer IV board with a "true"
centronics parallel port.
In the meantime, however, I've become interested in doing the thing
"right". I first thought that maybe the 8088 could despool from some
extra memory while the 8085 listened to me. No such luck. Godbout's
8085/88 dual processor board is constructed so that only one of the
processors may be active at once.
Now, I'm sort of thinking that it might be nice to have a slave
processor on the S100 bus. This processor might be able to handle
one or more of the following tasks.
- buffer printer output and despool it to any printer (I've got a
daisywheel as well as the Epson).
- spool information coming across my modem to my micro (i.e. catch
a long file in a local buffer).
- despool information from my micro to the modem (i.e. buffer a
file from my system to a buffer and then despool that to the
modem.
I know this technique will involve more expense than simply
purchasing an outboard buffering device. It also, however, sounds
like more fun and more flexible. Using this sort of scheme, I should
be able to cancel printing from my keyboard (by sending the
appropriate message to the despooler). Outboard despoolers usually
require a mechanical reset to clear printing.
Has anyone built such a despooler?
Does anyone have any comments about any of the available S100 SBCs
(single board computers) which might be applicable? I suppose
that I'll want to have a "slave" processor as my despooler
so that it doesn't put memory requests (and the like) out on the bus.
Jeffrey Stone
Menlo Park, CA