7800 GTX SLI: Double The Fun
The GeForce 7800 GTX is NVIDIA's latest flagship video card, and as such, it brings with it full support for the company's proprietary SLI (Scalable Link Interface) technology. We're not going to go in-depth with regard to the virtues of NVIDIA SLI because we've covered the technology in the past (see: here, here, and here), but there are some points we want to drive home to clear up some common misconceptions with regard to SLI.
By now, you should all know that SLI is NVIDIA's multi-GPU technology that gives users the ability to link two cards together to share a 3D workload. Theoretically, in GPU-bound circumstances, running two GeForce cards in SLI mode can offer up to a two-fold increase in performance. But many people have been misled to believe SLI only works with a select few games and applications. While it is true that NVIDIA's drivers only incorporate pre-tested SLI profiles for certain applications, users can easily create their own profiles to run virtually any application in SLI mode. Performance won't always scale, and determining which SLI mode (AFR - Alternate Frame Rendering or SFR - Split Frame Rendering) is correct could take some trial and error, but SLI is easily enabled for any application with a few clicks of the mouse. Plus, some developers have started designing games that enable SLI 'out of the box' that require no NVIDIA profile at all.
Some also believe that NVIDIA SLI will only work when using two identical video cards. This is also false. Any two similar cards from the same AIC partner will work together in SLI mode; they just have to be based on the same GPU. So, if you buy one card now and another later, they can work together in SLI mode. We should mention that NVIDIA has stated that this should change with future driver revisions, which they've said will allow the use of two cards from different AIC partners.
NVIDIA is also evangelizing the fact that SLI directly affects image quality by giving users the ability to play their games at higher resolutions, with features such as anti-aliasing and anisotropic enabled. On top of the ability to game at higher resolutions, NVIDIA also mentioned to us that a new anti-aliasing mode is on the horizon that incorporates a new SFR rendering technique with a combination of 4X multi-sample and 4X super-sample anti-aliasing. NVIDIA is labeling this new AA mode "16X AA." We were told it should be made available in a future driver release.