I'm a laptop user running Heroes of Newerth on an AMD Turion 2x2Ghz. When I play, in groups of 30 seconds (usually) it switches between 100% maximum frequency 25% maximum frequency (according to to win7's resource monitor).
More aboutslight problem maximum frequency
In control panel, go to power management/change advanced power settings and look at what is there. It is possible to set the minimum cpu % to 100% which will set the multiplier to the max which is probably what you want for games.
I already did this . It literally is like a step function with vertical lines connecting the steps for the graph of the maximum frequency.