CP/M survey - test-drb@ccmp.vtda.org

19 Apr 2007

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Subject: CP/M survey
   From: Mark Tapley <mtapley at swri.edu>
   Date: Wed, 18 Apr 2007 09:09:45 -0500
     To: cctalk at classiccmp.org

DEC Rainbow (8087, 832k (max for -A model), but  that's irrelevant to CP/M-80).

 Not true as the rainbow also ran CP/M-80/88 as it
 was a dual CPU (has a z80).

 Allison 
 Could it access more then 64k under CP/M-80? Don't
 you mean CP/M-86? Not to nit pick...
 I don't know about specific Rainbow revisions, but I
was under the impression the 'bow could go up to 896k.
Maybe I'm thinking of the Tandy 2000 via an 3rd party upgrade. 
I think Mark was trying to say that an 8-bit CP/M program on the Rainbow 
can only access 64k RAM, which is true, under Rainbow CP/M-86/80.  A 
16-bit program could access all of the Rainbow's system RAM under CP/M.

And he's also right about the memory.  A 100A maxed out at 832k, while a 
100B/100+ maxed out at 896k.  This is because 100A models shipped with 
128k on the motherboard, while 100B/100+ models shipped with 192k.  So 
when a maxed-out ram expansion card was installed, the 100A still had 64k 
less than an equivalent 100B/100+.

One interesting thing about 16-bit programs on CP/M-86/80 on the Rainbow 
was that some were confused by too much RAM.  The most notable examples 
are all the Rainbow ports of Infocom adventures; they all complain about 
"not enough memory" if you have more than 512k or something like that.

Jeff Armstrong
jba at sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org