Counter-Strike: Source uses the same engine as Half-Life 2 (refer to our Half the Way to Half-Life 2: Counter Strike: Source Benchmarked review for details).
The more advanced graphics cards hit against the performance ceiling set by the central processor in the “pure speed” modes. In higher resolutions, however, you can discern that the RADEON cards are one step ahead of the same-class GeForce cards, save for the GeForce 6600 GT.
The GeForce 7800 GTX SLI, GeForce 7800 GTX and GeForce 6800 Ultra SLI deservedly occupy the top positions on the podium, but ATI RADEON X850/X800 enjoy an advantage in the lower product categories.
The Piranesi scene is somewhat more difficult, but produces the same results: the ATI products are better than their respective rivals from the NVIDIA camp, save for the RADEON X700 PRO.
When we turn on FSAA with anisotropic filtering, even the GeForce 6600 GT which has earlier been faster than the RADEON X700 PRO falls behind it. The gap between these two cards amounts to 15% in 1600x1200.
SLI technology works fine in Counter-Strike: Source, but there’s not much sense in using it with the GeForce 7800 GTX – the performance of the system CPU becomes the limiting factor. As for the GeForce 6800 Ultra, you can achieve the level of the single GeForce 7800 GTX by joining two such cards. The less advanced SLI configurations are not that efficient. For example, the GeForce 6600 GT SLI performs worse than the single GeForce 6800 GT, so there’s not much sense in using that configuration.