This is far more exciting, since it adds functionality to they system. Maybe I'll dust off my old hacked up NES and do this at some point. If only I had the free time these days.
Thx for sharing :)
The most notable one I have seen was the performance change on Road Rash on the Genesis/Mega Drive. RR1 & 2 it just speed up the whole game. RR3, it just increased the frame rate and made it a much more enjoyable experience.
Sometimes you get sprites disappearing by priority, sometimes the software will alternate active sprites; software sprite disabling in some titles is probably harsher than needed (might flicker when there's more than X sprites on the screen, even if there is never more than 8 on one line)
The game only has a limited amount of time to do all of its logic before the VSYNC interrupt forces it to draw to the screen. Game have different ways of handling this, e.g. by rolling back and abandoning the changes, drawing whatever they have, etc.
A faster clock should make it s/t games that don't always get done in time should at least have a better chance.