XT/370 microcode

[Dave Wade]

Some of the code is now on bitsavers..

 

Dave

 

From: Eric Smith <spacewar at gmail.com> 
Sent: 12 March 2018 14:41
To: Dave Wade <dave.g4ugm at gmail.com>; General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Cc: Lars Brinkhoff <lars at nocrew.org>
Subject: Re: XT/370 microcode

 

On Mon, Mar 12, 2018, 05:13 Dave Wade via cctalk <cctalk at classiccmp.org <mailto:cctalk at classiccmp.org> > 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.