Well over a year ago I attended an ATI press briefing and was approached by an ATI PR representative that had obviously read some of my columns about NVIDIA’s SLI. He commented that I must’ve been on NVIDIA’s payroll when I wrote them as obviously SLI was never going to materialize and if it did, it would be haunted by problems. He continued his rebuttal by stating that ATI would never be tempted to try such a solution, as there is no market for it. Only a few months later I reminded him of those words at another press briefing where ATI had just announced that they’d also try their hand at a multi-GPU solution right after the successful introduction of NVIDIA’s SLI.
He told me that unlike NVIDIA’s, ATI’s multi-GPU solution will not require two identical cards to work, but can use any combination of Radeon Xx00 series PCIe graphics cards. Furthermore ATI’s solution will not require game profiles to be created, but offers a boost in performance with every game, right out of the box. Furthermore ATI’s multi-GPU solution will offer superior image quality without loss of performance at every resolution and last but not least would outperform NVIDIA’s solution by a significant margin. Bold claims to make at that time, as ATI had just decided to go head to head with NVIDIA on this a matter of weeks previously, specifications of this new platform had yet to be finalized I imagine.
This week we’ve witnessed the introduction of ATI’s multi-GPU solution now officially christened CrossFire. By the looks of it, the above claims haven’t materialized in the actual product. Unlike previously stated you can’t team up just any two Radeon Xx00 series graphics cards. You’ll need a master graphics card that connects to any Radeon Xx00 graphics card. Although that’s unfortunate, there’s more. Suppose you bought a Radeon X850 master card, which is a 16-pipeline card and team it up with a 12-pipeline card such as the Radeon X800. You’ll effectively lose one of the rendering modes, super-tiling, as well as dumb down the master-card as it is now only able to use 12 of its 16-pipelines. The opposite is also true, hence when you use a Radeon X800 master card, and team it up with a Radeon X850 XT card you’ll dumb down the slave card. So in order to make full use of all of CrossFire’s features and guarantee the best performance identical cards are needed.
Another claim made by ATI which also hasn’t materialized into the product is the fact that CrossFire would be able to accelerate all 3D applications without the need for application-specific profiles. In essence this only holds true when CrossFire defaults to scissor rendering mode for OpenGL and super-tiling rendering mode for Direct3D applications - and the latter is only available when identical graphic cards are used. In order to get the larger performance payoff of alternate-frame rendering or other load-balancing techniques, ATI does in fact rely on application profiles through their Catalyst A.I. software which is virtually identical to how NVIDIA uses profiles to up the performance with SLI.
One of the biggest obstacles however is the fact that CrossFire can’t render at more than a 1600x1200 resolution with a 60Hz refresh rate. I do not need to tell you that such a low refresh rate is headache inducing on anything other than flat-panel displays. Many people that are potential customers for CrossFire are the die-hard gamers that mostly use CRTs still, so this is a major drawback. Although ATI downplays this limitation by stating that gamers don’t use these higher resolutions much I’d have to disagree. It is at these higher resolutions that the benefits of a multi-GPU solution are really starting to show. More importantly however, gamers that use big, 19” and up, CRT monitors probably won't appreciate being confined to the headache-inducing 60Hz refresh rates at a maximum 1600x1200 resolution, especially since NVIDIA's SLI doesn't share this limitation.
And last, but certainly not least, performance is not up to today’s standards. Although two Radeon X850 graphics cards combined offer similar performance to two GeForce 6800 Ultra graphics cards that score is rather moot. NVIDIA’s new architecture, and the graphics cards based on it, the GeForce 7x00 series, have been out for almost six months now, hence the bar has been raised considerably. A CrossFire platform equipped with two Radeon X850 graphics cards has trouble keeping pace with a single GeForce 7800 GTX in most cases and is simply put to shame by two GeForce 7800 GTs in SLI. So although CrossFire has delivered on most of the basic goals they set for their multi-GPU solution it currently is hardly competitive. NVIDIA’s SLI has proven to be more elegant, flexible and currently offers better performance. We’ll reserve judgment until the new X1800 series of cards are introduced however. They could well negate some of the drawbacks of the current CrossFire implementation. But if not, then I guess CrossFire is indeed too little, too late.