Minimal CP/M SBC design?

Jim Battle frustum at
Mon May 5 16:52:20 CDT 2008

Ethan Dicks wrote:
> I was a bit young for the earliest days of CP/M, so in my mind,
> "traditional" was the era of packaged systems like Osbournes
> and Kaypros.  My mistake.  I even have a XOR 5-slot S-100 box
> at home, a gift from an older gentleman who happened to mention
> something to a relative of mine who works at the Post Office, but
> that's a long story - the short of it is that I have enough hardware
> to get it working, but no 8" CP/M disks, let alone the right
> one for that machine.

This page of mine has information on the XOR computer, including a 
couple of disk images that will get you running.  The disk images came 
courtesy of fellow list member Jerry Wright.

At the time I obtained the computer, I found very little information 
about it on the web, which is why I started the web page.  I had 
disassembled the monitor ROM before obtaining the original source. 
There were a couple spots in the code that didn't make any sense to me, 
  thinking perhaps my ROM had dropped some bits.  Once I had the source 
code, I found it really was a bug in the original monitor.  While the 
XOR used a Z80, the code was written with an 8080 assembler and some asm 
macros to handle some Z80-isms.  The correct macros were "PUSHIX" and 
"POPIX", but the coder wrote "PUSH IX" and "POP IX", resulting in bad 

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