Subject: Re: CP/M survey
From: Jeffrey Armstrong <jba at sdf.lonestar.org>
Date: Thu, 19 Apr 2007 12:08:11 +0000 (UTC)
To: cctalk at
classiccmp.org
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.
Of course and I referred to that. What I avoid trying to do was say, hey
it's a Z80 and 8bitters like 8080 and Z80 without only address 64k. Granted
you can hang bank hardware on them and extend but the addressing is
still only 64k.
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.
Unlike PCs were 640k was all there was.
Allison