Funny story.
My older brother had to disable one of the "processors" on his dual core to play San Andreas. (You can tell Windows to run certain programs with only one processor, Also in this menu there are tick boxes for 31 processors....)
If he didn't, the game ran TWICE as fast, making it totally unplayable.. but hilarious to watch.
Cars on the highway went so fast you couldn't see them untill they hit something, but they piled up HELLA FAST if you caused an accident.
The pistol was a machine gun, walking was faster than riding a bike at normal appication speed.
It was awesome!
My Pentium D doesn't do it though. Just his AMD I forget what.