I have a fx 8320 @ 4.4ghz a gigabyte 990fxa ud3 rosewill green 630 watt power supply. I have no idea why its doing this my temps are completely fine I also tried the plus %20 percent power thing and it still doesnt help.
It's quite possible that the game periodically does need more computing power from the graphics cards. The game and the settings used has a lot to say about that.
It usually starts at 99 percent but like 5 times a second switches between 64 percent and 99 percent its really wierd it looks very similiar to a saw wave if you look at it on the graph in afterburner.