Really bad SLI performance with benchmark applications

[Wolfman [TWP]]

I get the same problem with SLI/Multi GPU mode. I'm running the same card GF7950 GX2. I've noticed this with the Doom3 benchmark. When running this card in single GPU mode, I get 100 FPS, @ 1280x1024 everything maxed. And when I enable the second GPU in the AFR/SFR modes the frame rates drop down to around 60 FPS. And when I use the AA mode, it drops even further. And this is with the 96.25 Beta drivers.. So there's still quite some room for improvement with that driver..

System Specs:
AMD (SKT AM2) Athlon 64 FX62 Dual Core
Asus M2N32 WS Pro Mother Board
4GB's Corsair Dominator DDR2 XMS2-8500 RAM (@ stock 800MHz - For the moment)
MSI NX7950GX2-T2D1GE
Fedora Core 5 with all the updates

[lynedavid]

Has anyone had any positive experciences with SLI under Linux?

[LubosD]

Just testing GeForce 7950GX2 with MultiGPU on.
Oh My God! Even VESA renders fonts faster than this.

[Wolfman [TWP]]

Originally Posted by lynedavid

Has anyone had any positive experciences with SLI under Linux?

Not from what I can tell (And from what I've read on these and other forums).. I got almost double the performance with my OLD 3dfx Voodoo 2 SLI setup I had (Or I should say still have). With the advancements now with both hardware and software, I would have expected better.. I don't expect double the performance but at least way better than running a single card/GPU.

If I remember correctly with the 87.74 drivers, the Nvidia settings utility didn't even acknowledge the second GPU, even when I didn't have it enabled. The 96.25 Nvidia settings utility at least does show that they both exist, even when the second GPU wasn't enabled, so that's a start.

Looks like I'll be running my games, using a single GPU only, until this stuff gets sorted out..

Wolf

[lynedavid]

Originally Posted by LubosD

Just testing GeForce 7950GX2 with MultiGPU on.
Oh My God! Even VESA renders fonts faster than this.

Fonts? I doubt MultiGPU will make fonts any faster! How about with OpenGL apps? or am i not getting a joke here?

[lynedavid]

Originally Posted by Wolfman [TWP]

Not from what I can tell (And from what I've read on these and other forums).. I got almost double the performance with my OLD 3dfx Voodoo 2 SLI setup I had (Or I should say still have). With the advancements now with both hardware and software, I would have expected better.. I don't expect double the performance but at least way better than running a single card/GPU.

If I remember correctly with the 87.74 drivers, the Nvidia settings utility didn't even acknowledge the second GPU, even when I didn't have it enabled. The 96.25 Nvidia settings utility at least does show that they both exist, even when the second GPU wasn't enabled, so that's a start.

Wolf

The V9 version of drivers support Quad SLI. why would they implement this unless there was some gain in performance?

Or is there some sort of trick we are missing?

[Wolfman [TWP]]

Originally Posted by lynedavid

The V9 version of drivers support Quad SLI. why would they implement this unless there was some gain in performance?

Or is there some sort of trick we are missing?

Your guess is as good as mine.. I've been though the SLI/Multi GPU setup area in the manual, forwards and backwards several times, and I can't see what I'm doing wrong.. I'm configuring everything to the letter.. (*shrug*)

Wolf

[lynedavid]

I'm looking at this from a software developers point of view and if i knew how to optimize my oplcations for SLI then i would.

I understand that SFR will only give me more fill capacity (in theory double and I am getting very little), but I want to use AFR to which should in theory also give an increase in vertex capacity. But for me AFR gives less performance than SFR (and less than single GPU), which just shouldn't be the case.

My application requires vertical refresh sync. Is this a problem with AFR?

[Wolfman [TWP]]

Originally Posted by lynedavid

I'm looking at this from a software developers point of view and if i knew how to optimize my oplcations for SLI then i would.

I understand that SFR will only give me more fill capacity (in theory double and I am getting very little), but I want to use AFR to which should in theory also give an increase in vertex capacity. But for me AFR gives less performance than SFR (and less than single GPU), which just shouldn't be the case.

My application requires vertical refresh sync. Is this a problem with AFR?

That's exactly what I'm seeing here with Doom3.. (I haven't installed other games yet, as this is a new system. As it will be interesting to see if other games are effected this way too) Granted I don't do any software development, but it will most likely mean the finished product will not perform as expected either.. Oh, and I don't use sync to vertical refresh at all..

[lynedavid]

Originally Posted by Wolfman [TWP]

That's exactly what I'm seeing here with Doom3.. (I haven't installed other games yet, as this is a new system. As it will be interesting to see if other games are effected this way too) Granted I don't do any software development, but it will most likely mean the finished product will not perform as expected either.. Oh, and I don't use sync to vertical refresh at all..

I've never tested with SLI in Windows, but i've seen benchmarks for many games and benchmark applications that show a real performance increase with SLI. In your opinion, is it only the Linux drivers that do not achieve the performance?

[Wolfman [TWP]]

Originally Posted by lynedavid

I've never tested with SLI in Windows, but i've seen benchmarks for many games and benchmark applications that show a real performance increase with SLI. In your opinion, is it only the Linux drivers that do not achieve the performance?

Same here, I haven't tested it in Windows either.. (Nor do I ever intend to).. Yes, so far only the Linux Drivers seem to have this problem.. To my knowledge.. (And from the tests that I've done so far)

I had a thought, that it's strange that companies like Pixa (Not sure of the correct spelling at this moment), who created the "Finding Nemo" videos, and many others. As they used Linux systems to create them.. I'd say that they most likely using Quadro cards in dual or quad SLI to do it.. And we can't seem to get it going on our measly GF 7x series of cards.. I find that really strange...

[lynedavid]

So, as it stands does SLI only work at its full potential with Quadro cards? Since there is relatively little difference between the cards then wouldn't this be a marketing stategy?

I'm using these GF 7850 for simulation applications, so its not out of the question to use Quadros.