CrossFire gaming performance
Once again, there's nothing between the ASUS and Gigabyte boards when a single GPU is in place.
When more Radeon HD 5870s come out to play, however, things get interesting. Using two cards in a CrossFire configuration certainly has its merits, with performance jumping significantly across all of our gaming benchmarks; Modern Warfare 2, for example, sees an 80 per cent boost.
From there on in, things aren't quite as clear cut. Certain titles - Battlefield: Bad Company 2, DiRT 2, Far Cry 2 and H.A.W.X - continue to see lofty gains when a third GPU is introduced, but Aliens vs. Predator sees little improvement and both Crysis Warhead and Modern Warfare 2 take a backward step.
Adding in a fourth Radeon HD 5870, meanwhile, is of little real-world benefit. Doing so brings a few additional frames per second on a couple of games, but certainly not enough to warrant the cost of another £315 graphics card.
Each Radeon HD 5870 is equipped with a 1GB frame-buffer, and we believe that memory limitations impose a ceiling on just how effective a multi-card setup can be, especially when tested at 2,560x1,600.
Whilst NVIDIA SLI may deliver different results, four-way CrossFire currently serves primarily as a source of bragging rights. And, if two- or three-way CrossFire delivers the best results, that's one of the UD9's most prominent features cast into doubt.