I did some military electronics work and in short...

CMOS based chips draw a little more at high temp than low because of some "leakage". But it's insignificant compared to the wattage that a CPU is dissipating when it's running a game. For discussion I'm peg the leakage of a CPU to be some 0.010 Amperes at 1.8 Volts and even if it goes up by 10 times, thats all of 0.18 Watts. Given some CPUs are now at 100 Watts, that's not an effect that I'd worry about.

Hope this answers that.