OpenGL is an area where NVIDIA cards have always excelled. It's really a shame this API is not used more extensively in games. Doom 3 and The Chronicles of Riddick: Escape from Butcher Bay are two recent titles that take advantage of OpenGL. While both games are a good way to showcase the power of this API and NVIDIA cards, I chose Doom 3 for this test as there was no SLI profile in the drivers for Riddick at the time. Support has been added in drivers later than the ones with which I benchmarked, however I did not want to re-run all of my tests with an updated driver package. Perhaps at a later time I might add Riddick as an addendum to this review.
All in-game settings were put to their maximums. I used the built-in timedemo function and three proper runs at each resolution and image quality setting to determine the average.
Doom 3 - Timedemo 1
Big differences here, almost a 50 percent improvement in some cases. I didn't bother to test 2x AA in this game because 1280x1024 with 4xAA/8xAF is perfectly playable, and I don't play Doom 3 with regularity anyway.
HALO
This was a chance to see how a slightly older title might be able to take advantage of very new technology. That said, Halo does sport some advanced graphical features, like support for pixel shader 2.0. This test called for use of the game's built-in benchmark. Unfortunately some of the advanced features in this game come at a price, and that is anti-aliasing cannot be used. Image quality benchmarks were run with 8x anisotropic filtering only.
Halo - Timedemo
Yet another very impressive showing by SLI here. If this is a regular game in your repertoire, crank up the resolution and go crazy. Dual 6600 GT cards will not disappoint.
OVERCLOCKING
Good, very good or even excellent performance often is not enough for the enthusiast. The hardware elite will want to extract every last bit of performance out of whatever hardware they have. Though I did not overclock my CPU for this test, I did want to see how an increase in video clock speeds would affect SLI performance. I did not test UT 2004 as this game is so CPU limited that any sort of clock speed increase benefited performance by less than 2 frames per second.
The stock clock speeds of the MSI GeForce 6600 GT PCI-Express is 300 MHz on the core and 500 MHz (1,000 effective) on the memory in 2D mode. Starting a 3D application ramps up the core speed to 500 MHz while memory remains unchanged. I tuned my clock speeds with NVIDIA's own Coolbits registry tweak.
Clock Frequencies
Testing of various applications allowed me to setting on a final overclocked value of 550 core/1100 memory. I've read user reports of much higher clocks, but this certainly is nothing to sneeze at. I tested overclocked settings at the maximum image quality level in previous tests at 1280x1024, which in my opinion, was the optimal setting at which to play games.
Overclocked Results - 550/1100
On top of the already solid SLI performance numbers in games that take advantage of it, overclocking provides either a marginal or significant additional performance boost.
