Benchmark Results: Quad-CrossFire!
Although we only have one Radeon HD 6990 in the lab, I was able to enlist the help of someone with two—someone who could test the mettle of four Cayman GPUs running cooperatively. He didn’t have the same benchmarks I typically run, but the following tests still showcase the potential of two boards.
Consider this an exhibition for now; until we’re able to test two 6990s in a case—any case, given the lack of specific guidance from AMD—it’s impossible to say how viable a pair of cards under load can actually be. We do know he measured 869 W of system power using the stock BIOS and 987 W with the overclocked firmware (that's two cards and a 5 GHz overclocked Sandy Bridge-based platform).
Crysis? Very high quality settings? 2560x1600 with 4x AA? More than 60 frames per second? Yeah, we’ve finally seen it all.
Far Cry 2 shows us that there is such a thing as too much graphics horsepower if your display configuration isn’t elaborate enough. Not even anti-aliasing can slow down two 6990s working cooperatively.
The only chart I didn’t include here was Resident Evil 5, which shows that AMD’s driver isn’t necessarily optimized for four-way CrossFire yet; there’s no scaling moving from one card to two.