Benchmark Results: Multi-Card Scaling
A single GeForce GTX 560 Ti dominated the Radeon HD 5870 and 6870 in Lost Planet 2, so the fact that a pair of these cards does the same in SLI is really no surprise.
More interesting, perhaps, is that the Radeon HD 5870 and 6870 are so close together. We saw the 6870 throwing down faster frame rates at 1680x1050 and 1920x1080 in single-card mode, with the 5870 passing its successor at 2560x1600. In CrossFire, however, the two 6870s regain a tiny lead at 2560x1600, demonstrating better scaling on the Barts-based boards.
Aliens Vs. Predator is a different story entirely. The Radeon HD 5870 was a second-place finisher at 2560x1600 in single-card mode, and it uses that advantage to take first place in our three-way comparison. The GeForce GTX 560 Ti and Radeon HD 6870 were nearly indistinguishable before, and again fall very close to each other in SLI and CrossFire.
The GeForce GTX 560 Ti got brutalized in single-card mode, and the two AMD Radeon combinations smack it down again in F1. The less expensive Radeon HD 6870 even manages to turn in faster frame rates with 8x MSAA enabled than the GTX 560 Ti without AA turned on.
Better scaling on the Radeon HD 6870 allows it to outperform the GeForce GTX 560 Ti in dual-card mode, despite the fact that the Nvidia card was faster at 2560x1600 in our single-card setup. More notable is that the Radeon HD 5870 trumps both other pairs of cards for a first-place finish in CrossFire.
We banged our head against walls for days trying to figure out the SLI/CrossFire issue ahead of Blizzard’s Cataclysm expansion launch. According to AMD, it released a CrossFire Application Profile update during or shortly after we finished testing. Nvidia still has a bug report indicating that scaling isn’t consistently where it should be. However, after a number of small patches to the game and hardware driver updates, we’re happy to report that it’s now possible to see scaling in the same Crushblow to The Krazzworks flight path used in our original coverage.
Nvidia might say that it isn’t seeing ideal scaling, but the performance of two GeForce GTX 560 Tis is good enough (with 8x AA enabled) to match two Radeon HD 5870s (without AA). The Radeon HD 6870s trail behind, consistent with what we saw in our single-card results.