XT/370 microcode

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.