The highly anticipated game S.T.A.L.K.E.R. makes use of a proprietary DX9 game engine, dubbed "X-Ray" by its developers. It features an advanced DX9 renderer with Defferred Shading capabilities, which allows the engine to draw a vast amount of dynamic light sources with correct materials and light ‘feedback’. Becuase S.T.A.L.K.E.R. does not have a built-in benchmarking tool, we tested the game using FRAPS at resolutions of 1,280x1,024 through 2,560 x 1,600 with the in-game anti-aliasing and anisotropic filtering options set to their maximum values, and with full dynamic lighting enabled. We should also note that 'grass shadows' were disabled due to the dramatic slowdowns this feature causes during gameplay.
At 1280x1024 and 1600x1200, the new Radeon HD 2900 XT simply got beat up by both types of GeForce 8800 GTS in our custom S.T.A.L.K.E.R. benchmark when running in single card mode. Even the slower of the two GTS cards was up to 30% faster the HD 2900 XT here.
An interesting thing happens in the dual-GPU tests, however. Running the HD 2900 XT is CrossFire mode results in much better scaling than SLI and the cards are able to blow past even the mighty GeForce 8800 Ultra SLI configuration. Looking at how the delta separating the platforms gets smaller as the resolution increases though, leads us to believe NVIDIA's got plenty of headroom left for this game, once their drivers are tweaked. Then again, so does ATI. There's no way their software team has been able to wring all they can from the R600 at this early stage of its existence.
At the XHD resolutions, the Radeon HD 2900 XT's earlier lead while running in CrossFire mode disappears as the pre-overclocked GTS is able to squeak past it at the highest res. And in a single-card configuration the HD 2900 XT continued to get pummeled here. We should also note that this game was considerably more jerky on the ATI hardware. Anytime the game had to load new data, the Radeons dropped into single-digit framerate territory, which significanly hampered the experience.