CrossFireX Arrives: First Look at 3 and 4 GPUs in 2 Card Setups

Final Words

Is multi-GPU really the future? Maybe. Advanced rendering techniques will increasingly require the use of persistent dynamic objects created on the fly, however, and this will likely continue to get in the way of scaling beyond two GPUs unless something fundamental in GPU design changes or graphics memory architecture is expanded to allow for easier sharing of the workload. We can also take away from all this that it is a much better idea to have a smaller number of high powered GPUs doing the work, as the return on investment for dual GPUs will be higher than adding more of a lesser card to a system.

Then of course there's the ubiquitous driver questions. It is one thing to make a driver that works with the current graphics libraries; it's another to make it work optimally in all situations. Taking a (nearly) fully optimized driver and extending support to two GPUs adds another level of complexity, and we're still seeing numerous titles released that don't have properly working SLI and/or CrossFire support until after a driver update (and sometimes a game patch as well). The situation with two GPUs is actually quite good these days, particularly if you're willing to search forums and other technical sites for information on tweaks to help performance prior to the inevitable release of new drivers. Unfortunately, CrossFireX takes a step back to the earlier days of CrossFire, and there are numerous titles where scaling is either nonexistent or at least much lower than we would expect. As we've seen in the results today, drivers matter - there's no other aspect of graphics as likely to help (or hurt) performance.

Drivers aren't the only concern at present, of course. The installation process for CrossFireX is far more involved - with more potential conflicts - than any other graphics solution we've used recently. Some of the issues we experienced may be related to the Skulltrail platform rather than specifically stemming from CrossFireX. That's something we will only be able to understand better with additional time. If you want our honest opinion, right now CrossFireX is sitting way out on the razor-sharp bleeding edge. When it works, the results can be very impressive. When it doesn't, the headaches, BSODs, uninstalling, reinstalling, and hacking that may be required is enough to make the best geeks cower in fear.

For now, the real benefit of multi-GPU is still going to be in achieving higher levels of AA with little to no performance decrease. We've already looked at ATI's Super AA, and there was a feature that didn't quite make it into Catalyst 8.3 that we'll want to look at when it arrives. In an upcoming driver, we will be able to enable edge detection with Super AA, which should lead to some insanely high antialiasing. While we tend to lean towards higher resolutions as a better option than higher AA modes (and suggest 4xAA with transparency AA as a good target), we will certainly look at this when it becomes available.

We aren't done with our investigation of multi-GPU technology and the impact of more than two GPUs on a system. There are issues we definitely need to go back and investigate more. For instance, does the ability to render four frames ahead significantly affect input lag? If multi-GPU technology really is the future of high-end graphics, we need to assess the current shortcomings so that we can understand what direction to take to get us there.