OpenGL game performance was measured using Doom 3 and Wolfenstein: Enemy Territory. The table below contains the graphics settings that were enabled for Doom 3.
Doom 3 Graphics Settings
The following bar chart is a comparison of the average frame rate of two GeForce 6800 GT's running in SLI mode to a single GeForce 6800 GT. The built-in demo1 demo was run with the driver controlled image setting at quality at resolutions of 1024x768, 1280x1024, and 1600x1200 with no antialiasing and with 4X antialising.
Doom 3 Performance
SLI provides faster performance across the board in Doom 3. The relative increase in the average frame rate over a single GeForce 6800 GT becomes greater as the resolution increases and 4X antialiasing is enabled - 35% at 1024x768, 61% at 1280x1024, and 77% at 1600x1200.
Note that the average frame rate of a single GeForce 6800 GT received a respectable 38 frames per second at 1600x1200 with 4X antialiasing enabled. Benchmarking provides us with an indication of actual gameplay performance and 38 frames per second may be considered "playable."
By recording the minimum frame rate during the benchmark run using Fraps, we can pinpoint areas that will cause a decrease in performance. The following benchmark results reinforce the benefit of SLI. In this test, the minimum frame rate was recorded, at a resolution of 1600x1200 with 4X antialiasing enabled, from the demo1 demo and three additional demos that were developed by the folks over at The Tech Report.
Doom 3 Performance
In each test case, SLI provided at least a 93% increase in the minimum frame rate over a single GeForce 6800 GT. The minimum frame rate more than doubled in the trdelta1 demo!
WOLFENSTEIN: ENEMY TERRITORY PERFORMANCE
Enemy Territory is free and was developed by Splash Damage. Derived from the popular Quake 3 engine, Enemy Territory is an entertaining World War 2 multi-player objective-based first person shooter with player classes. Version 2.60 was released last month and features optimizations, in-game support for anisotropic filtering, and a Macintosh client.
Enemy Territory Graphics Settings
The following demo is from a multi-player game on the Radar map and takes around 30 seconds to complete. Note that the high quality image setting was enabled in the ForceWare driver control panel, which disables trilinear and anisotropic filtering optimizations.
Enemy Territory Performance
Today's high-end graphics cards are capable of running the Quake 3 engine at high resolutions with 4X antialiasing enabled at playable frame rates. To take advantage of SLI in Enemy Territory, image quality was further increased by enabling 8XS and even 16X antialiasing (using RivaTuner)!