Borderlands
This is my favorite game in a long, long time, so I had to use in it our latest CPU test suite. Borderlands is based on Unreal Engine technology and includes a built-in performance test, which we used here. We tested with the game set to its highest quality settings at a range of resolutions. The results from the lowest resolutions will highlight the differences between the CPUs best, so I'd pay the most attention to them. The higher resolution results demonstrate what happens when the our GeForce GTX 260 graphics card begins to restrict performance.

With these frame rate averages, Borderlands looks to run quite acceptably on all of the processors tested. Those especially low minimum frame rates, which don't vary by more than a few ticks from 20 FPS, appear to be a quirk of the game's built-in performance test. Playing the game on one of these systems, you won't feel such lows often.

The Clarkdale processors perform relatively well here, as the Core i3-540 beats the prior dual-core champ, the Core 2 Duo E8600. Notably, though, the Core i5-750 edges out the i5-661; buying a fast dual-core for gaming might still be a solid option, but at the same price, the Core i5-750 is faster in this game.

Left 4 Dead 2
We tested Left 4 Dead 2 by playing back a custom demo using the game's timedemo function. Again, we had all of the image quality options cranked, and we tested with 16X anisotropic filtering and 4X antialiasing. The game's multi-core rendering option was, of course, enabled.

Clearly, any of these CPUs can slice through L4D2 with ease. Relatively speaking, the Core i5-661 trails the Phenom II X4 965 and the Core i5-750. The Core i3-540 is better positioned against its price competitors, with a clear lead over both the Athlon II X4 630 and the rather unfortunate Core 2 Duo E7600.

Notice something here. Despite a clock-speed deficit, the Core 2 Quad Q9400 nearly matches the Core 2 Duo E8600. Likewise, the Athlon II X4 630 outright beats the Phenom II X2 550, though it's handicapped with lower clock speeds and less cache. The performance differences are minor in the grand scheme, but they signal a changing of the guard: no longer is a higher-frequency dual-core processor the superior option in games. We saw quad-core processors perform relatively well in our first round of Windows 7-based CPU tests, and these results further the trend.

Of course, what happens at higher resolutions here is a classic example of a GPU bottleneck taking over. If your graphics card becomes the primary performance constraint, having a faster CPU won't get you much.