IIRC, the original 64C (before the Rev E mobo) used a combination of 8500- and 6500-series chips. The Rev E mobo used all 8500-series chips and denser RAM chips (two 64k x 4.) It also eliminated the original 82S100-based PLA with a much larger, MMU-like logic array.
God, bus decoding on the 64 was fun! Multiplexing address space in the $DE00 and $DF00 pages was the best!
From memory, so I wouldn't necessarily quote me on this fact. Unfortunately, I've never owned a Rev E mobo. Would love to grab a couple, though.
The C64 just got better and better as time went on, to many degrees. With the notable exception of the sound chip. The 8580 dropped the 12v requirement and changed the filtering capacitors so the sound output was affected rather dramatically: certain instrument sounds became stronger and much clearer, while other effects suffered. The speech in Space Taxi, for instance, did not sound as good on the early 8580s as it did on a 6581R4.
I can't wait until I get my personal computer recreation room set up. It's been long enough!
