You might be right on the lesser clock ticks being used, Gorgonops. But that would be strange as they are supposed to run at the same rate of clock ticks per op code.

Just to throw confusion into the mix - there are 5 or so 6502s: the 6502, 6502A, 6502B, 6502C (Not to be confused with the 65C02), and 6502D. In these the differences is in how fast they can be clocked. Many accelerators like the ZipChip used the 6502C and 6502D; older ones that ran at 2MHz used the 6502B. It was interesting to see them developed, to back they did not go further, a 25MHz 6502 would simply kick ass! (IMHO.)