Date   : Sat, 13 Oct 1990 00:06:55 GMT
From   : zephyr.ens.tek.com!tektronix!nosun!techbook!fzsitvay@beaver.cs.washington.edu (Frank Zsitvay)
Subject: CP/M BIOS source language Was Re:Need help with S100

In article <1990Oct12.000849.12599@news.clarkson.edu> demarem@clutx.clarkson.edu
writes:
>I suspect that your choices for an OS are CP/M or CP/M :-).  You
>can probably order documentation and/or CP/M drivers for your
>devices, but you may have a bootstrap problem..you need the system
>running CP/M in order to modify CP/M for the system.  One nice thing
>about CP/M is that the BIOS sources (in assembler) come with it
>so you ought to do okay.  I would recommend aquiring the following
>items (to run on another system while getting your S-100 up):
>
>8080 cross-assembler
  
  An 8080 cross assembler on a cp/m machine??  go figure...

>Small-C (8080 version, source code is available, I have seen it in
>         *very* old Doctor Dobbs Journals, and believe that some
>    user groups have it available in machine readable form).
   NO!

   Don't do this!  Bad idea.

   you don't want to write a bios in c.   you're only restricted to
a maximum address space of 64k, so your bios has to be as small and
as fast as possible.  this is very important if you plan to add
double density drives to the system, since that requires some form
of sector blocking/deblocking.  you do that in c and the bios will
be much larger than it needs to be.  the best tools to use when writing
or hacking a bios is either ASM (which comes wth cpm) or RMAC, DR's
relocating macro assembler.  the job is easier with RMAC because it 
will generate your DPHs and DPBs for you.  My cpm mentor tells me MASM
will not work for this.

>
>Interestingly enough I happen to have a Z80 S-100 system running
>CP/M right here (part of my collection of anachronistic computers,
>I hardly ever use it, it sits next to an 8088 system which is next
>to an 80286 system, which is the most modern thing I own, and only
>because the University issued it to me when I enrolled).  Do not
>even dream of trying to run MINIX on an 8080 or Z80 system, it is
>pretty near impossible.
>
 I agree...

-- 
fzsitvay@techbook.COM - one of these days i'll get it right...

Version 2 of anything is usually the version that works.