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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mmntech - Saturday, March 8, 2008 - link
I'm running an HD 3850 256mb and I get 40fps average in low density areas, 12.4fps in London. Ultra quality of course with no AA and in game AF at 1440x900. That's DirectX 9.0 performance, which is all I could test since I don't run Vista. Flight Simulator has always been very CPU dependent, particularly concerning autogen scenery, and AI traffic along with the complex physics engine. Since FSX with SP1 can take advantage of up to four CPU cores, it might be worth starting off there. I did my tests using an Athlon 64 X2 3800+, everything at stock speeds with 2gb PC3200. If I were you, I'd go with the single 3870 X2 card. Cheaper than buying two separate 3870s. For nVidia, maybe two 8800GTS 640mb cards in SLI or better if you want the best performance. I'd wait for nVidia to release the 9800GX2 first though to see what cards offer the best performance per dollar.As for the article, I really wonder if using more than two cards is really practical. You can get almost the same performance with two 9600GTs as with three or four HD 3750s but the two 9600GTs are far cheaper. This begs the question, is spending the extra $400 really worth it for such minimal gains? I know for some it is but then why buy mid-range cards when a couple 8800GTXs will cost the same in the end. Plus there's also the increased heat and power consumption from using four cards instead of two. I'd like to see more info on that.
Incisal flyer - Monday, March 10, 2008 - link
Thanks for the replies derek anm mmntech. Mmntech, yes my feelings exactly about quad (basically) crossfire. I'm no computer geek (more like a newbie really - I don't understand understand most of what I read in the forums and couldn't overclock a toaster if you held my mother hostage). Multiple crossfire sounds just too exotic at this point and would be more headache than it is worth. Thanks for your feedback and happy flying.The Flyer
DerekWilson - Saturday, March 8, 2008 - link
i'm looking at fsx acceleration for future graphics articles ...no promises, but i've been testing it internally.
Sundox - Saturday, March 8, 2008 - link
isn't multi GPU the cheap way to go?I'm asking this because I can't figure a car race won by two slower cars, against the faster car, or two knifes cutting my steak smoother.
to me, it looks like the problem is,... coping with the problem, the companies just want to have the most powerful GPU, not the most efficiant.
I might be totaly wrong.
coldpower27 - Saturday, March 8, 2008 - link
It's more like a delivery race rather then a car race, who can deliver the total shipment fastest?Two smaller trucks pulling half the load each, or a single truck pulling a larger load, the larger truck's engine is more complex, and hence more difficult to build, vs the smaller trucks which have smaller engines which are easier.
Griswold - Saturday, March 8, 2008 - link
Analogies like that do not always work just like that.Besides that, the car race example isnt that simple anyhow. Imagine a 24h race which could easily be won by even one slower car, as long as it is more reliable than the faster one. Remember, in order to finish first, one must first finish. This, of course, has little to nothing to do with video cards, hence, analogies dont always work.
legoman666 - Saturday, March 8, 2008 - link
analogies almost never work.DerekWilson - Saturday, March 8, 2008 - link
"Like a balloon, and... something bad happens!"Simon128D - Saturday, March 8, 2008 - link
I love the reviews and benchmarks here, I really do but I'm getting sick and tired of seeing the test system being only a super high end machine with hardware that the average person can't afford and I think benchmarking with skull trail on its own is silly. Tis applies to other site as well.Don't get me wrong, I enjoy seeing benchmarks from a high end system like skull trail but how many people actually have or can afford a system like that. I'd like to see more of a mid range setup inculded in graphics benchmarks - that will give a more realistic view point. A system say with a 780i or X38 chipset with a Q6600 and 4GB DDR2 800Mhz etc.
Just my thoughts.
DigitalFreak - Saturday, March 8, 2008 - link
It's really the only way to make sure the games they're testing with aren't CPU limited.