"CP/M compatible" vs. "MS-DOS Compatible" machines? - test-drb@ccmp.vtda.org

3 Feb 2008

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Subject: Re: "CP/M compatible" vs. "MS-DOS Compatible" machines?
   From: "Roy J. Tellason" <rtellason at verizon.net>
   Date: Sat, 02 Feb 2008 20:54:28 -0500
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On Friday 01 February 2008 03:36, Jim Battle wrote:
(Snip)
  Also, people did *plenty* of ugly stuff to save a
few bytes back then,
 as you know.  RST1 isn't particularly ugly anyway.  And if for some
 reason one did find it unpleasant, you could use a macro to make it to
 your liking. 
Yup...

(Snip)
  we agree.  :-)  I had a vague recollection of a
faint memory of hearing
 third hand that CP/M was ported to some heathkit machine, but that the
 machine already had a ROM in low memory, and so instead of "CALL 0005H",
 one had to use "CALL 2005H" or some such.  CP/M programs could be very
 easily reassembled/patched for this, but stock CP/M binaries wouldn't
 work.  rather than repeating this slanderous story, I didn't bring it up
 and pretended it was just a supposition.  ooops, but now the cat is out
 of the bag. 
I believe the H-8 did indeed have a ROM at low memory.  Never worked with that 
machine,  though.  There were also some TRS-80 boxes that I seem to recall 
having a need of a special version of CP/M as well. 

TRS80 (original) had the first 16k used for rom, keyboard and videoram,
Therewas a hacked version of CP/M for it that moved page 0 (first256bytes) 
to something like 4200h and TPA started arond there too.  The problem was
none of the usual CP/M programs were assembled/compiled to start at 4200h
(norm was 0100h) and even if the trs80 was full of ram you were under 48k
which was ok but bigger CP/M apps like MSBASIC used some 24K of that or 
more.  Not a popular implmentation.

Allison

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