A Look At Triple-GPU Performance And Multi-GPU Scaling, Part 1
by Ryan Smith on April 3, 2011 7:00 AM ESTClosing Thoughts
Unlike our normal GPU reviews, looking at multi-GPU scaling in particular is much more about the tests than it is architectures. With AMD and NVIDIA both using the same basic alternate frame rendering strategy, there's not a lot to separate the two on the technology side. Whether a game scales poorly or well has much more to do with the game than the GPU.
| Radeon HD 6970 | GeForce GTX 580 | |||||
| GPUs | 1->2 | 2->3 | 1->3 | 1->2 | 2->3 | 1->3 |
| Average Avg. FPS Gain | 185% | 127% | 236% | 177% | 121% | 216% |
| Average Min. FPS Gain | 196% | 140% | 274% | 167% | 85% | 140% |
In terms of average FPS gains for two GPUs, AMD has the advantage here. It’s not much of an advantage at under 10%, but it is mostly consistent. The same can be said for three GPU setups, where the average gain for a three GPU setup versus a two GPU setup nets AMD a 127% gain versus 121% for NVIDIA. The fact that the Radeon HD 6970 is normally the weaker card in a single-GPU configuration makes things all the more interesting though. Are we seeing AMD close the gap thanks to CPU bottlenecks, or are we really looking at an advantage for AMD’s CrossFire scaling? One thing is for certain, CrossFire scaling has gotten much better over the last year – at the start of 2010 these numbers would not have been nearly as close.
Overall the gains for SLI or CrossFire in a dual-GPU configuration are very good, which fits well with the fact that most users will never have more than two GPUs. Scaling is heavily game dependent, but on average it’s good enough that you’re getting your money’s worth from a second video card. Just don’t expect perfect scaling in more than a handful of games.
As for triple-GPU setups, the gains are decent, but on average it’s not nearly as good. A lot of this has to do with the fact that some games simply don’t scale beyond two GPUs at all – Civilization V always comes out as a loss, and the GPU-heavy Metro 2033 only makes limited gains at best. Under a one monitor setup it’s hard to tell if this is solely due to poor scaling or due to CPU limitations, but CPU limitations alone do not explain it all. There are a couple of cases where a triple-GPU setup makes sense when paired with a single monitor, particularly in the case of Crysis, but elsewhere framerates are quite high after the first two GPUs with little to gain from a 3rd GPU. I believe super sample anti-aliasing is the best argument for a triple-GPU setup with one monitor, but at the same time that restricts our GPU options to NVIDIA as they’re the only one with DX10/DX11 SSAA.
Minimum framerates with three GPUs does give us a reason to pause for a moment and ponder some things. For the games we do collect minimum framerate data for – Crysis and Battlefield: Bad Company 2 – AMD has a massive lead in minimum framerates. In practice I don’t completely agree with the numbers, and it’s unfortunate that most games don’t generate consistent enough minimum framerates to be useful. From the two games we do test AMD definitely has an advantage, but having watched and played a number of games I don’t believe this is consistent for every game. I suspect the games we can generate consistent data for are the ones that happen to favor the 6970, and likely because of the VRAM advantage at that.
Ultimately triple-GPU performance and scaling cannot be evaluated solely on a single monitor, which is why we won’t be stopping here. Later this month we’ll be looking at triple-GPU performance in a 3x1 multi-monitor configuration, which should allow us to put more than enough load on these setups to see what flies, what cracks under the pressure, and whether multi-GPU scaling can keep pace with such high resolutions. So until then, stay tuned.
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Sabresiberian - Tuesday, April 5, 2011 - link
I've been thinking for quite awhile that we need something different, and this is the primary reason why - I can't get all I want to install on any ATX mainboard I know of.;)
Sabresiberian - Tuesday, April 5, 2011 - link
I've always thought minimum frame rate is where the focus should be in graphics card tests (when looking at the frame rate performance aspect), instead of the average. It's the minimum frame rate that bothers people or even makes a game unplayable.Thanks!
;)
mapesdhs - Wednesday, April 6, 2011 - link
I hate to say it but with the CPU at only 3.33, the results don't really mean that much. I know
the 920 used can't go higher, but it just seems a bit pointless to do all these tests when the
results can't really be used as the basis for making a purchasing decision because of a very
probably CPU bottleneck. Surely it would have been sensible for an article like this to replace
the 920 with a 950 and redo the oc to 4+. The 950 is good value now aswell. Or even the
entry 6-core.
Re slot spacing, perhaps if one insists on using P67 it can be hard to sort that out, but there
*are* X58 boards which provide what one needs, eg. the Asrock X58 Extreme6 does have
double-slot spacing between each PCIe slot, so 3 dual-slot cards would have a fully empty
slot between each card for better cooling. Do other vendors make a board like this? I couldn't
find one after a quick check on the Gigabyte or ASUS sites. Only down side is with all 3 slots
used the Extreme6 operates slots 2 and 3 at 8x/8x; for many games this isn't an issue (depends
on the game), but I'm sure some would moan nonetheless.
Would be interesting to know how that would compare though, ie. a 4GHz 950 on an Extreme6
for these tests.
Unless I missed it somehow, I'm a tad surprised Gigabyte don't make an X58 board with this type
of slot spacing, or do they?
Ian.
xAlex79 - Thursday, April 14, 2011 - link
I am a bit disapointed Ryan in the way you put your conclusions.At the start of the article you highlight how you are going to look at Trifire and Tri-Sli and compare how it does for the value.
Yet at the end in your conclusion there isnt a single mention or even adjusted scores considering value at all. And that makes Nvidia look alot better than they should. It is as you completely forget that three 580s costs you 1500$ and that three 6970s costs you 900$.
Based on that and the fact YOU stated you would take value into account (And personally I think posting any kind of review without value nowdays is just irresponsible and biased) I am very disapointed with an otherwise very good set of tests.
I also understand that this is labeled "Part 1" and that the value might come into "Part 2" but you should have CLEARLY outlined that in your conclusion were that the case. And given the quality of reviews that we have come to expect from Anantech, the final numbers should ALWAYS include a value perspective.
I will jsut outline that it is poor form and not very professional and that in the end the people you should care about are us, your readers. Not how you look or try to look for hardware manifacturers. If this was a mistake, you should correct it asap. It does not make you look good.
L1qu1d - Friday, April 15, 2011 - link
I wonder why they didn't opt for the 270.51 Drivers and went with 3 month old drivers?Compared to the tested drivers:
GeForce GTX 580:
Up to 516% in Dragon Age 2 (SLI 2560x1600 8xAA/16xAF Very High, SSAO on)
Up to 326% in Dragon Age 2 (1920x1200 8xAA/16xAF Very High, SSAO on)
Up to 11% in Just Cause 2 (1920x1200 8xAA/16xAF, Concrete Jungle)
Up to 11% in Just Cause 2 (SLI 2560x1600 8xAA/16xAF, Concrete Jungle)
Up to 7% in Civilization V (1920x1200 4xAA/16xAF, Max settings)
Up to 6% in Far Cry 2 (SLI 2560x1600 8xAA/16xAF, Max settings)
Up to 5% in Civilization V (SLI 1920x1200 8xAA/16xAF, Max settings)
Up to 5% in Left 4 Dead 2 (1920x1200 noAA/AF, Outdoor)
Up to 5% in Left 4 Dead 2 (SLI 2560x1600 4xAA/16xAF, Outdoor)
Up to 4% in H.A.W.X. 2 (SLI 1920x1200 8xAA/16xAF, Max settings)
Up to 4% in Mafia 2 (SLI 2560x1600 AA on/16xAF, PhysX = High)
Fony - Thursday, April 28, 2011 - link
taking forever for the Eyefinity/Surround testing.vipergod2000 - Thursday, May 5, 2011 - link
The one thing that erks me is that the i7-920 OCed to ~3.3Ghz - causing the scaling of 3 cards being greatly reduced as opposed to other forum users that have 3 or 4 cards in CFX or SLI but with fantastic scaling - but assured with a coupling a i7-2600k at 5ghz minimum or a 980x/990x at 4.6ghz+