Some of the code is now on bitsavers..




From: Eric Smith <> 
Sent: 12 March 2018 14:41
To: Dave Wade <>; General Discussion: On-Topic and 
Off-Topic Posts <>
Cc: Lars Brinkhoff <>
Subject: Re: XT/370 microcode


On Mon, Mar 12, 2018, 05:13 Dave Wade via cctalk < 
<> > wrote:

. Wikipedia says there were/are
2x68000 CPU's..


One Motorola chip was the custom one, the other was normal (as indicated by 
mask code). There was also an Intel math co, presumably derived from 8087.


I used to have an AT/370, which had the same chipset, but I was never able to 
obtain the software.


I very strongly suspect the modified 68000 and 8087 have more than just 
microcode differences, and that full reverse-engineering of the die would be 
necessary to accomplish anything useful with the microcode. Neither chip was 
designed to be a general-purpose microcode engine; both were very heavily 
tailored for their exact visible architecture, and 370 architecture is enough 
different that it couldn't be implemented by microcode only changes with no 
data path changes; the microcode ROMs and PLAs just aren't big enough to work 
around the data path issues.


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