I have updated the: https://gunkies.org/wiki/KD11-E_CPU https://gunkies.org/wiki/KD11-EA_CPU articles with the DEC part numbers for the i) microcode and ii) instruction decode PROms. That's not all the PROMs on the Control card - there are effing bazillions of the damned things (I suspect they used them to reduce the amount of random logic, so the CPU'd fit on two boards) - but it's most of them. I have yet to triple-check them, so there might still be transcription error or two. I wouldn't be too sure of that; silence so far. I have reached out to Mike Douglas, to ask where the microcode dump on DeRamp came from: perhaps the originator can help with the missing bits. (Although perhaps I should ask Al K; BitSavers also has the dump, and it's older, so perhaps that copy came All of them? Or is just one failed? I'm wondering if you've just had a single one lose a bit or two; that's somewhat common in old PROMs. The chip you reported as failing (E111) almost certainly couldn't have taken out an instruction decode PROM, it's nowhere near them. I ask because we have absolutely nothing on those PROM's contents. With the microcode PROMs, we at least have the contents in symbolic form (see pg. 15 of MP00082; alas, we don't seem to have the KD11-EA equivalent of Table 7-15 Absolutely nothing. But if they're _mostly_ there, with the partial contents, and a description of the failure mode (e.g. 'SETC doesn't set the C bit'), we might be able to work out what bit got dropped. Failing that, someone's going to have to volunteer to unsolder a set, and read them out - at least, I assume that's what would have to be done. Perhaps a logic analyzer could be attached to an instruction decode ROMwhile the CPU ran diagnostics, and eventually a complete readout of the contents accumulated. Noel