Measuring CPU scaling performance with the Core i7-3770K from 2.5GHz through 4.5GHz revealed just a 6% increase in performance (97fps to 103fps) with the Radeon HD 7970 GHz Edition. This suggests that owners of Core i7 and possibly Core i5 processors need not worry about overclocking, as little is gained in Warfighter.
When measuring performance changes when shifting the AMD FX-8350 from 2.5GHz to 4.5GHz, we found a 12% gain -- twice that of the Core i7-3770K. Nonetheless, given that the FX-8350 operates at 4GHz by default, there's still not much to be gained from overclocking.
Looking at a range of AMD and Intel chips side by side reveals that most quad-core or greater processors provided similar performance in Warfighter. Unsurprisingly, the Core i7-3770K took the top spot while the overpriced i7-3960X was a close second along with the FX-4170.
However, most CPUs allowed the HD 7970 GHz Edition to render between 94 and 98fps, which is only a 4% difference in performance. Dipping below 94fps was the Phenom II X6 1100T with 93fps, the i7-920 with 92fps and the i3-3220 with 91fps.
Beyond that, frame rates started dropping off rapidly, with the Athlon II X4 640 averaging just 85fps followed by the Phenom II X2 560 at 82fps and the Athlon II X2 265 with 78fps. Warfighter is optimized for quad-core processors and there is a noticeable performance dip when using a dual-core chip.