I don't think the clock speed of the GPU has anything to do with the frame
rate of the game. In fact, most games intentionally limit themselves to 60
FPS, and some of them intentionally limit themselves to something even lower,
like 30 FPS. Going higher than 60 FPS is pointless visually, though it does
improve responsiveness of the controls, which is why I chose 120 FPS for a
Pong game I wrote with the SGE Game Engine.
That being said, I'd like to point out that frame rates above 24 FPS do make
a substantial difference in games. There are a couple of reasons, but the
biggest one is speed. The effective speed limit for any given object is the
relevant size measurement of the object per frame, because moving any faster
can cause collisions to be missed. So for example, a 32 pixel wide object is
effectively limited to moving horizontally 32 pixels every frame without
causing collision bugs. This effectively means that such an object can move
at a rate of 1920 pixels per second at 60 FPS, but only 960 pixels per second
at 30 FPS, and a paltry 640 pixels per second at 20 FPS. The effect becomes
more significant with smaller objects.
This has actually been a problem I've had to work around in ReTux, which
through delta timing can run at as low as 20 FPS -- if the fireballs and ice
bullets had bounding boxes as small as you would expect, they would have to
move much slower than they currently do, and the fact that they're already
moving at their effective maximum speeds has meant that I've had to forgo
conservation of momentum for them.
