Battlefield 3 paints an interesting performance picture. Equipped with a GTX 260, the difference between dual and quad-core configurations is tiny -- and actually favors the 3GHz Conroe. Once we switch to the GTX 660, the tables turn. The GTX 660 delivers a respectable 15% performance boost for the E6850, but the Q6600 pulls ahead in absolute terms.
Overclocking the Q6600 improves the CPU's performance enormously. The gain is noticeable even without Fraps; the game is much smoother.
Borderlands 2 doesn't have presets, so we've dropped in a handy screenshot with the settings we used.
In Borderlands 2, we forced FXAA on via the graphics driver as well as enabling it from in the in-game menu. This somewhat improved the visual quality but didn't impact performance much on either card.
In Borderlands 2, the Q6600 has a significant performance advantage with both GPUs. The E6850 + GTX 260 combination is slow enough to drag noticeably when there's a lot of action on the screen; the Q6600's frame rate dips at these moments, but not to the same degree. Switching to the GTX 660 gives the E6850 a 60% frame rate increase, compared to a gain of 50% for the Q6600. Here, the benefit of overclocking is fairly modest -- a 25% clock speed boost yields a 12.5% performance gain.