Date   : Thu, 23 Aug 2007 20:27:22 +0100
From   : julesrichardsonuk@... (Jules Richardson)
Subject: M512 copro schematics?

Eelco Huininga wrote:
> Jules Richardson wrote:
>> It's a substantially different animal to the 80186 board it seems... 
>> (...)
> 
> Some time ago I disassembled the 80186 BIOS, and found out that it was
> written for both the 80186 and 80286. There are some code which checks the
> processor type. Since then I've been wondering if the 80286' BIOS is in
> fact the same as the 80186'. Have you ever compared the '186 and '286
> BIOSses to see if they are the same?

Hiya,

The way I was told it, Acorn did the M512 ROM development work on the 80286 
machines - basically because they had the handful of ABC3xx machines that had 
been built lying around unused (the whole ABM line was pretty much a dead end 
by that time, with only a few ACWs actually sold) and it made more sense to 
use those as a starting point.

Presumably at one time, in the early days of the 80286 boards, there was a 
specific ROM for the machine - but I was told that all the '286 systems ended 
up with the 'hybrid' ROMs once they got pressed into service for development 
work.

It's interesting though that some '286 code survives in the M512; I'm 
surprised it didn't evolve over time. I'll try comparing what I have at some 
point - unfortunately my '286 board ROMs are hex dumps and my M512 ones 
(actually for the 1MB version) are binary, and trying to figure out the 
necessary format string for the hexdump utility so that I can compare them has 
given me a headache :-)

cheers

Jules