A Look At Triple-GPU Performance And Multi-GPU Scaling, Part 1
by Ryan Smith on April 3, 2011 7:00 AM ESTMass Effect 2, Wolfenstein, and Civ V Compute
Mass Effect 2 is a game we figured would be GPU limited by three GPUs, so it’s quite surprising that it’s not. It does look like there’s a limit at around 200fps, but we can’t hit that at 2560 even with three GPUs. You can be quite confident with two or more GPUs however that your framerates will be nothing short of amazing.
For that reason, and because ME2 is a DX9-only game, we also gave it a shot with SSAA on both the AMD and NVIDIA setups at 1920. Surprisingly it’s almost fluid in this test even with one GPU. Move to two GPUs and we’re looking at 86fps – again this is with 4x super sampling going on. I don’t think we’re too far off from being able to super sample a number of games (at least the console ports) with this kind of performance.
Wolfenstein is quite CPU limited even with two GPUs, so we didn’t expect much with three GPUs. In fact the surprising bit wasn’t the performance, it was the fact that AMD’s drivers completely blew a gasket with this game. It runs fine with two GPUs, but with three GPUs it will crash almost immediately after launching it. Short of a BSOD, this is the worst possible failure mode for an AMD setup, as AMD does not provide individual game settings for CF, unlike NVIDIA who allows for the enabling/disabling of SLI on a game-specific basis. As a result the only way to play Wolfenstein if you had a triple-GPU setup is to change CrossFire modes globally, which requires a hardware reconfiguration that takes several seconds and a couple of blank screens.
We only have one OpenGL game in our suite so we can’t isolate this as an AMD OpenGL issue or solely an issue with Wolfenstein. It’s disappointing to see AMD have this problem though.
We don’t normally look at multi-GPU numbers with our Civilization V compute test, but in this case we had the data so we wanted to throw it out there as an example of where SLI/CF and the concept of alternate frame rendering just doesn’t contribute much to a game. Texture decompression needs to happen on each card, so it can’t be divided up as rendering can. As a result additional GPUs reduce NVIDIA’s score, while two GPUs does end up helping AMD some only for a 3rd GPU to bring scores crashing down. None of this scores are worth worrying about – it’s still more than fast enough for the leader scenes the textures are for, but it’s a nice theoretical example.
| Radeon HD 6970 | GeForce GTX 580 | |||||
| GPUs | 1->2 | 2->3 | 1->3 | 1->2 | 2->3 | 1->3 |
| Mass Effect 2 | 180% | 142% | 158% | 195% | 139% | 272% |
| Mass Effect 2 SSAA | 187% | 148% | 280% | 198% | 138% | 284% |
| Wolfenstein | 133% | 0% | 0% | 151% | 96% | 145% |
Since Wolfenstein is so CPU limited, the scaling story out of these games is really about Mass Effect 2. Again dual-GPU scaling is really good, both with MSAA and SSAA; NVIDIA in particular achieves almost perfect scaling. What makes this all the more interesting is that with three GPUs the roles are reversed, scaling is still strong but now it’s AMD achieving almost perfect scaling on Mass Effect 2 with SSAA, which is quite a feat given the uneven scaling of triple-GPU configurations overall. It’s just a shame that AMD doesn’t have a SSAA mode for DX10/DX11 games; if it was anything like their DX9 SSAA mode, it could certainly sell the idea of a triple GPU setup to users looking to completely eliminate all forms of aliasing at any price.
As for Wolfenstein, with two GPUs NVIDIA has the edge, but they also had the lower framerate in the first place. Undoubtedly being CPU limited even with two GPUs, there’s not much to draw from here.
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Castiel - Monday, April 4, 2011 - link
Why didn't you just use a P67 board equipped with a NF200 chip for testing? Using X58 is a step in the wrong direction.UrQuan3 - Monday, April 4, 2011 - link
Mr Smith,When you do the multi-monitor SLI\Crossfire review, could you briefly go over different connection modes? The last time I messed with SLI, it forced all monitors to be connected to the first card. Since the cards in question only had two outputs, I had to turn off SLI to connect three monitors. This caused some strange problems for 3D software.
Would you go over the options currently available in your next review?
Ryan Smith - Monday, April 4, 2011 - link
When was this? That doesn't sound right; you need SLI to drive 3 monitors at the present time.UrQuan3 - Thursday, April 7, 2011 - link
Right this second I'm typing on a PC with 2 GTX 260s (not sure which revision) with two monitors plugged into the first and a third monitor plugged into the second. At the time, SLI would only allow monitors plugged into the first card. Of course, since IT doesn't trust us to do our own upgrades, I'm still running driver version 260.89.Of course, Windows supports multiple dissimilar cards with a monitor or two on each, even different brand cards. However, 3D support in this mode is, er, creative. In this mode most programs (games) can only drive one card's monitors. You can, however, have different programs running 3D on different cards' monitors.
Since you'll have the hardware sitting on your desk, I'd love to see a quick test of the options.
BLHealthy4life - Monday, April 4, 2011 - link
How the heck did you get 11.4 preview to work with crossfire??I have 6970 crossfire and I cannot for the life of me get 11.4p to work. I have used 11.2 and 11.3 with no problems. I removed previous drivers with ATI uninstaller followed by driver sweeper. Then I've installed 11.4 p 3/7 and 3/29 and neither one of them work.
I even went as far as to do TWO fresh installs of W7 x64 Ultimate and then install 11.p and the f*cking driver breaks crossfire....
Ryan Smith - Monday, April 4, 2011 - link
I'm afraid there's not much I can tell you. We did not have any issues with 11.4 and the 6970s whatsoever.quattro_ - Monday, April 4, 2011 - link
did you use DOF when benching METRO ? i find the HD6990's score high! i only get 37fps average : 980x @4.4 and single hd6990 stock clocks and 11.4 preview driver .Ryan Smith - Monday, April 4, 2011 - link
No, we do not. Metro is bad enough; DOF crushes performance.ClagMaster - Monday, April 4, 2011 - link
I will never understand why people will by 2 or 3 graphics cards, require a 1200W power supply, so they can get 10-20 fps or more subtile eye candy.There are some things that are beyond the point of reason and fall into the madness of Captain Ahab. This is just about as crazy as insisting on a 0.50 cal Browning Target rifle than a more sensible 0.308 Win Target rifle for 550m target shooting and white tail deer hunting. The 0.308 Win is less punishing on the body and pocketbook to shoot than the 0.50 Browning.
I always believed in working with one (1) graphics card that takes up 1 slot and requires 65 to 85W of power. A 9600GT plays all my games on a 1600x1200 CRT just fine.
looper - Tuesday, April 5, 2011 - link
Excellent post... well-said.