[rescue] [OT] S: IBM /370 or /390 card

[Lionel Peterson]

Emulating a 68000 to emulate a 370?

At some point it starts to resemble the light 'hack' in an early big-bang theory episode:

https://youtu.be/onZ4KMM94yI?si=AZGAKQr5QvL3yZrD

I mean I get it, but...

Ken

> On Sep 12, 2023, at 16:46, Joshua Boyd via rescue <rescue at sunhelp.org> wrote:
> 
> On 9/12/23 16:37, Dave McGuire via rescue wrote:
>> On 9/12/23 16:25, Mouse via rescue wrote:
>>>>> Wasn't the XT/370 primarily made with 68000s with custom microcode?
>>>>> [...] I'd love to see someone work out how to redo that on a newly
>>>>> made board.
>>>> Since the 68K's control store is in mask ROM on the chip, I think
>>>> that would be a challenge.
>>> 
>>> I can't imagine that there would be any difficulty beyond possible lack
>>> of documentation in reimplementing a 68k with writable microcode in a
>>> modern FPGA.
>> 
>>   How I interpreted Josh's question was the modification of a 68K's microcode.
> 
> 
> I was originally thinking modify the microcode in the chip, but making a cycle accurate microcode compatible 68K in an FPGA to run altered microcode would also be cool.  Extra cool if the FPGA's image was derived from a scan of the 68k silicon.  Square the cool if that was then run through on one of Google's Open MPW shuttles.
> 
> I haven't dug into it too deeply, but I think that when people talk about emulating 68000s as part of, say, the MiSTer project, they are using a fairly high level emulation of 68000s, not something that is executing original microcode. I guess it would be interesting to know what is really happening there.  Also how far down the accuracy hole the MAME 68k core goes.
> 
> 
> 
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