Performance Update - ATI CrossFire

Final Thoughts

As you might have suspected, judging CrossFire was never going to be an open and shut case and once again we’re left with a mixed bag of results with which to make an assessment from.

It’s clear at least from performance in Fallout 3 and S.T.A.L.K.E.R.: Clear Sky that CrossFire can work superbly – we’ve seen stunning frame rates and scaling, especially from a pair of cut-price HD 5770s that frequently outperformed the £300 HD 5870. Scaling of over 90 per cent despite the overheads of a multi-GPU setup is serious impressive feat and in these two titles CrossFire categorically delivers.

It’s not all great news though – Crysis offers smaller performance improvements for those who double up on their GPU and while CrossFire offers roughly 60 per cent scaling in Crysis, the GTX 285 in SLI offers over ninety percent scaling in comparison. Yes, there’s still a marked improvement over single card performance, but it’s much less attractive than the numbers from Fallout 3 and S.T.A.L.K.E.R.: Clear Sky.

Looking at Dawn of War 2 and Call of Duty: World at War though clearly shows the other side of the CrossFire coin. Performance slower than a single card from a multi-GPU setup, especially in games that been on release for over nine months each is unacceptable. A pair of HD 5870s - £600 worth - in CrossFire is actually slower than a single £120 HD 5770 when it comes to minimum frame rates in World at War. What’s equally disappointing is that the multi-GPU improvements we saw in Dawn of War 2 for the HD 5970 haven’t yet been carried over to the Catalyst driver, leaving all our CrossFire setups again outmatched by single cards.

We also noticed that CrossFire setups, somewhat unsurprisingly, ran notably hotter than their single card versions. The 5870 in particular runs over 30°C hotter when in CrossFire when at load, although whether this is a Catalyst driver setting, the proximity of the nearby second card or the larger workload isn’t clear. What is clear though is that hotter cards also mean louder cards too – HD 5770s in CrossFire were clearly audible in our labs while the single card was pleasingly quiet and the same goes for the HD 5850. While we're sure many won't mind it's an important thing to consider, especially when we were testing an extremely well ventilated Antec 1200.

CrossFire CrossFired?

We hope it’s clear then that Multi-GPU setups still have a way to go, and unsurprisingly it’s once again drivers and compatibility that has let CrossFire down rather than the lack of GPU grunt.

For every Fallout 3 and S.T.A.L.K.E.R.: Clear Sky there’ll be a Dawn of War 2 or Call of Duty: World at War, and those who are considering a CrossFire setup should carefully consider the pros and cons. There’s also the fact that new games won’t necessarily be supported straight away by Catalyst drivers, leaving you waiting until the next month’s release for multi-GPU support, until which you’re left with performance that could quite possibly be worse than a single GPU.

There are green shoots though. In comparison to previous multi-GPU group tests this one has been blissfully easy going, with none of the stability or reliability issues that have previously plagued both SLI and CrossFire. That’s not to say that multi-GPU is now fool-proof but we’ve definitely seen a massive improvement in reliability in both CrossFire and SLI compared to this time last year.

There’s also the undeniable fact that when it all clicks into place both CrossFire and SLI can offer huge performance improvements, although often you've got so much power on tap you need a very fast CPU and a huge monitor to get the best out of them.

For us, right now there’s still too much uncertainty when it comes to CrossFire and compatibility to make us seriously consider recommending grabbing two cards over a more powerful single GPU model. While the potential is there, in practice more work is needed on the driver side before CrossFire becomes a must-have upgrade. A faster single GPU such as the HD 5850 or HD 5870 is still the way forward.