Maybe stupid question

The problem is, most older 3D console games (pre-DreamCast; with exceptions of course) use the frame rate itself for their timers. At a given time the frame rate can be very accurately predicted, thanks to the closed nature of a console, so the developers used to attempt to sustain a cap frame rate (usually 30 on PSX/N64, but now most games are 60 - substitute 25 and 50 for PAL), and run perfect at that frame rate, but reductions in the frame rate result in the infamous 'slowdown' effect... rather than stutter, the game actually slows down because the world sampling ends up being drastically slowed down.

Or something along those lines. But anyway, most of the time, if you get the frame rate too high you'll end up in overspeed.

Now there are of course exceptions on both PSX and N64... and even some post-DC games use the frame rate (BAD!)... but in general that should hold true-ish.