Thanks a lot! I understand why wou don't want to crack them out - but it would be great if you could just remove the Rainbow's "baking tray" and take pictures of the mainboard and cards - this would allow us to crossreference your dump with the actual chip parts.
I took several pictures, but this one is the one that came out best. The part numbers are indeed different than the other 100As. And there's a lot of rework on this board, more than I would have though would have shipped. And the green socket one of the chips is in looks funky to me....
So these are 23-090E4-011-24, 23-091E4-011-24 and 23-092E4-011-24. So this beast must be an earlier version / late prototype. I bought it from someone who told me their son got it when it first came out and he was maybe a salesman for DEC (I think he and his son had been estranged and he was tasks with disposing of his estate because he had a lot of weird stuff from the 80s). The number of rework wires (maybe 2 dozen) also suggests this isn't the final production version...
Another potential shortcoming of this method is that debug can't reach the chargen ROM and Z80 arbitation PROMs that are in MAME's ROM definition as well.
I might consider this... I half remembered the BIOS EEPROMs were funky in some way which is what put me off removing them... Now that I've opened it up again, I see why... The characters look the same, so I'd be a little hesitant there, but would consider the Z80 arbitration PROMs. Do you have a pointer to the 100A schematics? I saw them online years ago, but google only shows me the 100B ones in bitsavers... I think I found the 6308 on the 100A and I'll see if my universal programmer can read it back before undertaking to remove and dump it... (I have a photo of it too, marked
if that helps. But the photo that it's in has 4 rework wires, including one that goes to a pin that's been lifted out of the board entirely...