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Old 20th Mar 2021, 9:02 pm   #1189
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default Re: Non-working Commodore PET 3016

I hope you're right, I would have expected it to score a few random hits though. Thinking possibly buffered R/W (UG7 pin 9) may be constantly high, which it should not be of course. Or shouldn't it? That's the default state for the R/W line when it is not writing. We have the CPU locked in read mode while doing the NOP test, so R/W steady high (therefore UG7 (8) steady low) may actually be OK.
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