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Old 18th Feb 2021, 7:50 pm   #601
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 7,092
Default Re: Non-working Commodore PET 3016

Clock divider UG5,
Address buffers UE9 / UE10,

Of these, UE9 and UE10 did appear faulty to a degree as their outputs were not really driving low enough.

UD7 was dud, the other three main PROMs were OK.

We still seem to have an apparent problem with the CPU reading one of the illicit 'KIL' instructions when all of the data lines are connected.

We have a bit of a catch-22 situation where we can't connect all the CPU data lines so we can't properly observe what is happening with the data bus buffers, or at least on certain lines on those.

Do we go for replacement of the data bus buffers, or try something else? A NOP test to exercise the address lines and chip selects, perhaps?
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