I suspect that's just the CPU going to lower-power states when the load is low. This should not affect performance at all, so it should not need a "solution."
------------------------------e2160@3GHz: OCing my way to Ubuntuland!
Reply to Mondoman
If you go into power settings and the advanced settings under high performance click on change settings, than click on change advanced power settings. A new window will pop up and you should be able to scroll down to Processor Power Management, varify that both minimum and maximum processor state are set to 100%.