CrossFire And SLI: DiRT 3, Metro 2033, And LuxMark
A second Radeon HD 7950 only adds 86% to the performance of just one GPU. That doesn’t change the overall finishing order, though. Two GeForce GTX 580s are faster, trumped by a pair of Radeon HD 7970s and then both of the quad-GPU configurations.
Although two dual-GPU Radeon HD 6990s have an edge on the Radeon HD 7950 CrossFire setup with 4x MSAA applied, the 7950s are actually faster using the Adaptive Anti-Aliasing mode. In the process, AMD’s latest skates right past two GeForce GTX 590s and 580s. Only the Radeon HD 7970s are faster.
Two Tahiti XT GPUs nearly match a quartet of Cayman processors in LuxMark. Scaled down to the Pro variant, you lose quite a bit of compute performance. However, a pair of Tahiti Pros still decimates four GF110s in this benchmark.