I have a working C128 desktop that I'm using to troubleshoot a non-working C128D-CR.
I suspected a problem with CIA 2 on the C128D, so I swapped its chip labelled "6526A" with a 1988 year stamp with the "6526A-1" from the flat C128 which has a 1986 year stamp. I was expecting these two chips to be interchangeable.
The suspect chip from the C128D failed to boot in the flat C128, thus confirming it is "bad". However, there was no change to the C128D when I installed the known good CIA in it.
SO I am left to wonder if there are TWO faults in the C128D. But before assuming that, I'm also wondering if these two "versions" of the 6526A are actually suppose to be interchangeable?