Has anyone looked into the possible failure modes of the CIA?
This has to be one of the most vulnerable components inside the C64
with little (or indeed, on the older boards, none) protection,
directly wired to connectors. Actually I have several dead C64's
that have either or both CIAs shot, so maybe I should start the
research myself, with those individual chips.
There are a few different possible scenarios. The worst is that
the whole chip gets fried either due to latch-up or if the static
charge is large enough to destroy other stuff besides the I/Os.
Somewhat more manageable would be, if only the I/O pins (one or many)
got fried, and the rest (timers, TOD, interrupt logic) still worked.
Then it shouldn't be that hard to make a simple adapter board with
latches, tri-state drivers, some glue logic and a socket for the
partially fried 6526.
After that, the only problem would be to find as many BROKEN 6526's
as possible and perhaps build a test jig to be able to determine
how broken the chip actually is.
Daydreaming? You tell me!
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