CrossFireX Arrives: First Look at 3 and 4 GPUs in 2 Card Setups
by Derek Wilson on March 7, 2008 12:05 PM EST- Posted in
- GPUs
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.
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MAIA - Tuesday, March 11, 2008 - link
"After rebooting a few times to let windows do its thing, we installed the driver and all was well."This sentence is soooooo microsoft windows !!! :))
Sorry .... had to say it.
dash2k8 - Tuesday, March 11, 2008 - link
I'm just wondering: instead of piling on the number of GPU's, why hasn't a manufacturer just come out with ONE monstrous GPU that does away with the need of using multiple video cards? If someone is crazy enough to spend moola on 4 GPU's, I imagine that person would be equally willing to buy ONE card that has the same horsepower. Just saying.punko - Monday, March 10, 2008 - link
Thanks Derek for a good review. As you indicated, this may be the future and its good to see the tech reach a point where it is ready for use and can be improved upon as all tech goes forward.It also sound like you had a lot of help directly from AMD on this one.
gsellis - Monday, March 10, 2008 - link
"but today a WHQL drier is available "Hey Derek, typo in the beginning. Still mirthful about this one. Water cooling and you needed it drier to work with all GPUs?
ltcommanderdata - Sunday, March 9, 2008 - link
I'm just curious as to whether you've checked to see if quad channel memory has any benefit for multiple GPU situations? With 3 or 4 GPUs sucking data, I would presume the additional memory bandwidth provided by quad DDR2-800 would increase performance, especially since dual channel FB-DIMMs are not as efficient as the best dual channel DDR2 or DDR3 setups on desktop boards. It would be interesting to see the results of a 4x1GB setup on Skulltrail vs the 2x2GB setup you used.cerwin13 - Saturday, March 8, 2008 - link
Would it be wise to try this upgrade without SP1 installed with Vista 32? I am currently using 2x Radeon HD3870 x2s and would like to benchmark with these new drivers, but apparently SP1 isn't officially out yet?DerekWilson - Saturday, March 8, 2008 - link
other people had luck without SP1; it's not a requirement, but some of our editors did find that it helped with a lot of stuff ...you'll want to make sure you have hotfixes:
929777-v2
936710
938194
938979
940105
945149
as a minimum
Ananke - Saturday, March 8, 2008 - link
XFX has Forceware 169.32, my guess it was added after 9600GT appear. On Nvidia official download site the highest ver is 169.28Ananke - Saturday, March 8, 2008 - link
XFX has Forceware 169.32, my guess it was added after 9600GT appear. On Nvidia official download site the highest ver is 169.28Incisal flyer - Saturday, March 8, 2008 - link
Derek, thanks for the very timely and detailed review. I'm going to be building a system for Flight Simulator X and have been trying to figure out the best graphics card(s) for that application. Have you considered benchmarking that sim? A lot of discussion right now on AVSIM etc on what to do in terms of GPUs for people building new systmes. There is a lot of back and forth on advantages and disadvantages of different configs. I realize FSX is a bit of a niche product. Would FSX use multiple GPUs like 2 3870 x2s and are the potential headaches of that configurtation worth it if you are a not a computer geek? Or am I better off just getting a couple of Nvidia 8800s in SLI or a single 3870 x2 and not hassling with the 4 GPU solution? Any help or advice would be appreciated. Thanks in advance for your time.Incisal Flyer