We ran a couple of games to see how much of an impact would be seen in real world applications. Here, we have World in Conflict, Unreal Tournament 3 and Quake 4, all run at 1024 x 768 with low settings and with AA/ AF disabled. This would remove the graphics card as the bottleneck.

World in Conflict proves to be very dependent on CPU performance and we see a 28% penalty in framerates.

 
In Unreal Tournament 3, we see an insignificant difference of 2 FPS.

In Quake 4, we see a fairly huge gap of 55FPS - a 31% difference in framerates.