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
