Because we're already working with significantly lower average frame rates (compared to the Intel processors), we don't need to test as many CPUs here. Overclocked to 3.7 GHz, our mystery Phenom II X6 isn't able to add any additional performance, suggesting that clock rate isn't our bottleneck here. In fact, it's the lack of cores and cache that seems to hurt the two Athlon II chips most.
Although every single benchmark result on this page is generated with the help of a GeForce GTX 480, frame rates drop under 40 FPS on the Athlon II X2 system. There's simply not enough processing horsepower in the Athlon II or Phenom II lineups to let our graphics card stretch its legs.
Could it be a problem with Nvidia's GPU? We dropped a Radeon HD 5870 in with our Phenom II flagship to check and came up with 59.19 FPS in the same test (a mere 1.31 FPS difference). Clearly, AMD's CPUs are holding back performance in Cataclysm compared to Intel's processors.