Due to the specifics of the new game engine from id Software, their Doom 3 prefers graphics cards with NVIDIA’s GeForce FX and GeForce 6 architectures as being more efficient with the Z-buffer and shadows. Moreover, Doom 3 makes use of the OpenGL API, whose support is implemented in NVIDIA’s driver better than in ATI’s.
The superiority of the GeForce 6 is beyond any doubt as the diagrams show. NVIDIA’s graphics cards are a cut above their rivals from ATI in all resolutions, yet we can’t say that the latter are too slow for a comfortable play. It’s less dramatic in the PCI Express realm, but the modest GeForce 6800 GT anyway outperforms the RADEON X850 XT PE. The GeForce 6600 GT, in both AGP and PCI Express incarnations, rules among mainstream solutions.
The advantage of NVIDIA’s cards shrinks a little in the “eye candy” mode, since ATI’s architecture is better suited to do full-screen anti-aliasing and anisotropic filtering. This goes for the top-end as well as mainstream class; the GeForce 6600 GT is still superior in the latter.
The RADEON X850 XT Platinum Edition delivers the performance of the GeForce 6800 GT, but these two devices belong to different weight categories (the official price of the GeForce 6800 GT is $399 against the ATI card’s official price of $549).
The SLI platform shows here what this technology is capable of when is correctly optimized for a particular game. The GeForce 6600 GT duo easily reached the level of the GeForce 6800 GT, while the system with two GeForce 6800 Ultra cards has absolutely best results, especially in high resolutions as well as in the “eye candy” mode.