XT/370 microcode

[Eric Smith]

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