Performance Update - ATI CrossFire

Performance Analysis

With eleven different card configurations on test there’s plenty to talk about, and in Fallout 3 in particular CrossFire seems to work excellently. Due to Fallout 3's relatively low hardware demands we’re hitting CPU limitations at resolutions such as 1,680 x 1,050 even with single GPU setups, but jump to 1,920 x 1,200 or 2,560 x 1,600 and things becomes much clearer, especially when looking at minimum frame rates.

At 2,560 x 1,600 the HD 5850 and HD 5770 in CrossFire both achieve over 75 per cent scaling (minimum frame rates) in comparison to single cards, with the HD 5870 in CrossFire likely limited by a 3.2GHz quad-core Core i7 CPU even at the highest resolution. A pair of HD 5770s in particular really impress, closely matching or outperforming the HD 5870 in every test – great going for a pair of cards that combined cost £240.

S.T.A.L.K.E.R.: Clear Sky is a game with a history of performing well using ATI hardware and that’s certainly the case with our CrossFire setups. The HD 5870 in CrossFire, is, unsurprisingly, an insanely powerful setup and is likely CPU limited until we switch to 2,560 x 1,600 where it scales incredibly well – 97 per cent scaling on the average FPS and 85 per cent scaling in terms of the minimum frame rate.

The HD 5850 and HD 5770 deliver similar scaling at lower resolutions, but jump to 1,920 x 1,200 and HD 5770 CrossFire hits a performance bug that drops it to the bottom of our performance charts and at 2,560 x 1,600 its minimum frame rates are disappointing. A pair of HD 5850s however is much better, offering superb scaling at every resolution and comfortably matching the HD 5970.


Dawn of War 2 is a game with a history of being unfriendly to multi-GPU setups but following some impressive performance in our HD 5970 review we thought perhaps ATI’s latest Catalyst drivers would turn this around. However, it’s obvious that whatever optimisations that have made it into the HD 5970s release driver aren’t yet in the publicly available Catalyst drivers, with all our CrossFire setups delivering miserable and even negative differences in performance when compared to a single card. It’s particularly marked when anti-aliasing is enabled, with improvements only occurring to average frame rates rather than minimums where it really counts.

Crysis is much more multi-GPU friendly and while it still obviously runs better on comparable Nvidia equipment (SLI GTX 285s comfortably outclass HD 5870s in CrossFire) the ATI CrossFire configurations all perform markedly better than single cards. The HD 5770 delivers roughly 60 per cent scaling on both average and minimum frame rates, with the HD 5850 and HD 5870 faring a similarly across the board. In comparison the GTX 285 in SLI delivers far better scaling of around 90 per cent at every resolution and AA setting.

However, we’ve saved the worst for last for ATI’s CrossFire, with our Call of Duty: World at War benchmark proving a disaster for ATI’s multi-GPU technology. While averages when using CrossFire all rise dramatically towards the in-game frame rate cap of 91fps, minimum frame rates are all woeful, and in the case of the HD 5870 CrossFire are less than half that what you'd get if you took one of the cards out of your system and just used a single card!

What’s even more galling is this isn’t some brand new engine but one that has been effectively unchanged for close to two years and the Catalyst 9.11s used by the HD 5770 CrossFire offer no improvement. While the CrossFire configurations all still deliver superb average frame rates, it’s the minimum frame rates that you’ll notice and it’s clear that CrossFire is a letdown here.