AMD's CrossFireX: Tri & Quad GPU Previewby Anand Lal Shimpi on February 21, 2008 3:00 AM EST
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Back when we reviewed the Phenom AMD really wanted us to stress the importance of CrossFireX as a part of the overall platform package. After all, only AMD 790 FX motherboards were properly equipped to support four GPUs and that was a clear advantage Phenom held over Intel's Core 2. We see this sort of pressure all the time; NVIDIA has been trying to get us to test with its "platforms" for the past year, with little success of course.
We never capitulate, always stressing that we'll use components because they make sense, not because they are a part of some platform that doesn't necessarily offer a tangible benefit to the end user. We strive for scientifically sound comparisons at AnandTech, testing ATI video cards on an AMD platform and comparing them to NVIDIA video cards on an NVIDIA platform would violate the scientific method in a horribly inappropriate way.
It's always a good thing that we don't capitulate, but it was extra good in the case of Phenom for one very obvious reason: CrossFireX didn't work. Upon Phenom's launch, CrossFireX was promised as a feature but the driver support was not ready. Even today, CrossFireX continues to be a feature that's been promised but not delivered.
What is CrossFireX? The new CrossFire is AMD's attempt to finally achieve multi-GPU parity with NVIDIA's SLI. And like NVIDIA's SLI, CrossFireX supports configurations of 2, 3 or 4 GPUs.
All the way down to basic marketing CrossFire has always fallen short of dethroning SLI, but AMD has been making significant strides towards perfection. The release of the Radeon HD 3870 X2 surprised us, as it was the most seamless multi-GPU implementation we've ever seen. The card just...worked. AMD promised a new world of multi-GPU support in the future after the release of the X2, and since that review we've started giving it the benefit of the doubt.
AMD plans on enabling CrossFireX support sometime in March (we also plan on being at CeBIT sometime in March, maybe the two will coincide), but in the interim we've been provided with a preview system to begin to whet our quad-GPU appetites.
Receiving such a system doesn't come without its caveats however. The graphics and chipset guys over at AMD are a bit frustrated, they finally have a competitive GPU and they never get tested on their own platforms because everyone uses Intel CPUs. Had Phenom been competitive at launch this would be a very different situation, but it wasn't, so it's not.
In an effort to give Phenom some more limelight, AMD built these CrossFireX systems with 790 FX motherboards and quad-core Phenom CPUs running at 2.6GHz. We were only allowed to run today's tests on this platform. (Shh...we never capitulate!)
When testing four GPUs we tend to run at very high, GPU bound, resolutions making the choice of CPU much less of an issue. If anything, AMD was hurting itself by forcing Phenom upon us but it figured that any performance deficit due to CPU choice wouldn't be too great thanks to the GPU-limited nature of most of the tests we'd be running.
The system, all AMD
The other stipulation for receiving this preview system is that we had to agree to only test the games AMD shipped with the system: Call of Duty 4, Bioshock, Unreal Tournament 3, Crysis and Half Life 2: Episode Two. AMD's explanation for why is as follows:
"We’ve chosen some apps that demonstrate the performance that these new configurations afford gamers, and the scalability that can be seen when moving from a single GPU to four GPUs. While these apps show good scaling, we haven’t selected these because they represent the “best-case scenario” – in fact, there are other games that exhibit better scaling, as your testing down the road will show. The five apps we’ve chosen are intended to be a fair representation of the CrossFireX experience in general. "
Certainly when it comes time to actually review CrossFireX we'll be able to test on our own system with whatever games we'd like, but for this preview we were limited to the titles mentioned above. Thankfully the titles AMD allowed us to test with were all parts of our regular suite and we do believe that the intention wasn't to paint CrossFireX as best as possible, but to avoid this preview turning into a list of games that didn't work.
Given the constraints, you should view this article much as the title indicates - a preview.