24 Apr
2007
24 Apr
'07
10:25 p.m.
Subject: Re: Hand-rolling a CP/M machine
From: "Ethan Dicks" <ethan.dicks at gmail.com>
Date: Tue, 24 Apr 2007 14:29:35 -0400
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
On 4/24/07, Allison <ajp166 at bellatlantic.net> wrote:
As I am.
One other thing.. CPUs..
I've only mentioned Z80s.
So far.
Others from the junkbox would be:
8080 (for the three voltage masochist).
Indeed. But the last 8080 I saw in the field was in a 1970s B&W video game.
8085 (Also makes for simple systems)
Those are somewhat common if you hang around DEC equipment. NSC800 run it if you got one.
Don't know that one - what makes it special? Z180
Z280
ez80 (in Z80 mode)
These all look like Z80 descendents to me - I'd probably rarely, if
ever, run across one to harvest. 8085s are
common and makes a fair CP/M system. One caveat is that some
(far from all) applicaions software expects a Z80 though, most run on 8080
and above.
Since the Z80 was rather prolific, and should still be easy to obtain,
either from junked equipment or just new for a couple of bucks from a
place like BG Micro, what would be the appeal of an 8085? Just a
variant on the theme, or is there something neat about it that
warrants investigation? Since a bit of the requirements of such a system turn
on the
applications' needs more than the operating system's needs, I can
throw into the mix that the things I'd probably most likely try to run
would be some flavor of BASIC, Wordstar, an Infocom engine, and most
likely a Scott Adams/Adventure International engine - pretty much the
sort of stuff I would have run in the late 1970s through the mid-1980s
if I'd had a CP/M system of my own. I'd say that a few hundred K of
removable storage and a 64 or 80-char-wide screen should take care of
all of those.
Infocom games are 80x24 for best results. For storage i'd advise at
least a 360k floppy (if you r doing floppy) as anything smaller is cramped.
CP/M programs and stuff bit larger (around 512k) storage systems easier.
the best example I give for that is:
Basic system, PIP ED,STAT, ASM, DDT, LOAD plus the CP/M BDOS assemble
and edit on one drive and between the .bak, Hex, OBJ, PRN you can easily
fill a 360k disk and then some.
So for storage (floppy) I always advise TEAC55F (or GFR strapped for 300rpm)
to get two side 80tracks and about 720/780k formatted. Or a 720K 3.5" floppy.
IDE disk makes the space issue go away as 8mb is a large drive for CP/M.
Allison