Multi-GPU Scaling Analysis
So, are two cards twice as powerful as one? Are three cards 50% better than two? We compared each two-way and three-way configuration to its own single-card scores to find out, and split the charts to remind readers that the GeForce GTX 570 SLI scaling analysis uses a GeForce GTX 570 baseline, while the Radeon HD 6950 CrossFire analysis uses a Radeon HD 6950 baseline.
Two HD 6950s are up to 78% better than one at 1680x1050, beating Nvidia’s 58% gain by a wide margin. A third GPU is nearly wasted by either technology at this setting, as we'd expect.
It takes three GeForce GTX 570s to match the scaling of two HD 6950s at 1920x1080. On the other hand, our previous page showed that Nvidia’s higher baseline made two-way configurations the only “proper” performance match.
Things get ugly for Nvidia at 2560x1600. While a 67% performance gain for two-way and 112% gain for three-way SLI certainly aren't shabby, AMD’s 92% two-way and 145% 3-way gains put it in the winner’s circle.
This, in spite of the fact that one of our games, Aliens vs. Predator, didn’t even benefit from the third AMD card.