I recall a few games where I've had to limit the processor speed.

The weirdest one was an old adventure point and click. It was either "The 11th Hour" or "The 7th Guest". It had a puzzle where you need to beat the CPU in a board game.

At the time it was released, it was possible. On a modern PC, not so much. The more powerful your processor, the more skilled the CPU was in the board game. Made it impossible.