Windows Vista and Multi-GPU Technologies: Pitfalls
Microsoft has acknowledged that its new and actively promoted operating system Windows Vista does not support multi-GPU technologies inherently. The OS does not redirect the driver’s draw requests to GPUs other than the main one. As a result, only one GPU is used no matter how many GPUs there are in the graphics subsystem, and you get an appropriate resulting performance.
Microsoft released a patch for Windows Vista to address the issue, but notwithstanding Nvidia’s claim that SLI works in the Vista environment, we could not make this technology work with any version of ForceWare available at the moment of our tests, including version 162.22. The appropriate option just did not appear in the ForceWare control panel irrespective of the SLI configuration.
As for the opposing technology, we could easily launch a CrossFire tandem using ATI Catalyst 7.7 and benchmarked its performance in games. So, we guess the Catalyst driver is just better optimized for Windows Vista.
ATI’s technology provided a considerable performance growth in most cases. When the growth was zero or even negative in certain applications, it was due to the specifics of the game engine, not to some incompatibility with Windows Vista. Thus, the situation with multi-GPU support in Windows Vista was like follows at the moment of our writing this review: solutions from the former ATI Technologies were fully operable while Nvidia’s solutions were not. That’s why we did not benchmark GeForce 8800 GTX SLI and GeForce 8800 Ultra SLI configurations for this review.