Hand-rolling a CP/M machine

[Allison]

>
>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:
>> 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.

As I am.

>
>> NSC800 run it if you got one.
>
>Don't know that one - what makes it special?

National did a odd mix of z80 archetecture and 8085 interface.
It's a Z80 for the programmer and 8085 like for the hardware
hack.


>> 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.

Z180s do end up in the stragest of places.

>> 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?

Z80s are easy to find/get as are 8085s.


>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