The cpu % option is more for games that use mysterious wait-states that haven't been figured out yet, for example:
cv1000, and maybe a few cps-1/2 games. It doesn't work on a lot of games, such as those that sync w/interrupts or sync to vdp.
I have an idea for a tas feature where input recordings would actually work, and it would work with -every- game:
An option to slow down the framerate, and some macro keys to select between like 25/50/75/100%
I've been thinking about how to impl. this for several years now. Might have to do some experiments soon!
best regards,
- dink