Re: CP/M for any Commodore

From: Ethan Dicks (
Date: 2008-03-18 15:13:50

On Tue, Mar 18, 2008 at 1:18 PM,  <> wrote:
> Hallo allemaal,
>  I found some old Z80 operated printer buffers. These are nothing more
>  then a Z80 CPU, some I/O to communicate with the printer(s) and the
>  attached computers, quite some RAM (256 KB IIRC) and the needed
>  glue-logic. I lately also got a CP/M box for the BBC. This is nothing
>  more then a 6522 and all the things mentioned above (although only 64 KB
>  RAM).
>  Attaching a 6522 (or 6526) to whatever Commodore shouldn't be a problem.
>  Finding a printer buffer with a Z80 could be a problem...
>  Next step is the software of course: a BIOS...
>  Is there any interest in this?

Strangely enough, yes.  I just ran across an old printer-switcher.
It's Z-80-based,
on three boards in a box, the CPU board (6MHz clock, 8K SRAM, 8K ROM, an
address GAL), then on a "kbus" connection, two I/O cards with two or three Z8420
PIO chips, a couple of '74 flipflops, and 2-3 parallel connectors
each.  I think it
would be trivial to trace out the CPU board and the 26-pin "kbus", then a)
bump it up to at least 32K of SRAM, and b) add some form of UART (I
have 16550s and 6402s within reach) for a console, then c) work out what to
do about mass storage.  With three or five (depending on what boards are
installed) parallel ports, a CF or IDE interface seems easy to implement.

If it makes sense to, it would be easy for me to slap a 6522 or two on the
card with the console UART... I happen to have a few lying around.  Less
common parts might be tough since I won't be able to get mail until
October, but at least I have a variety of reasonable parts to start with.

Just the other day, I was thinking about what it would take to turn this
box into a CP/M machine.  I decided that I had enough other projects
on my plate, but with collaboration, it might be worth considering.

Oh... these boards are dated 1985, made by Protec Microsystems.  The
CPU board is marked "AS3-CPU" and "PMS34-7".  The two parallel boards
are marked "AS3-PAR" and "PMS35-13".  The box was re-sold by Black
Box as an SW805A "Auto Parallel Switch IV".  It has a 9VDC 1A input
jack and is about 22cm x 10cm x 6cm - roomy, but nice and portable.
The boards are 100% through-hole, 2-layer: easy to work on and trace out.


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