CUDA Multi-GPU Question

[UpstartXT]

I have a thread here: http://forums.anandtech.com/showthread.php?p=31373004&posted=1#post31373004 in general hardware about building a rig for video editing (premiere, After effects, etc.)

I have 3 monitors so we were thinking dual GPUs, 450 GTSs to be exact, since these have CUDA functionality but don't need to be top of the line gaming since I will be doing zero gaming on this computer.

We were wondering, does a second GPU in any way contribute to performance via CUDA or any other way in the video editing/rendering process?

 

[3DVagabond]

I have a thread here: http://forums.anandtech.com/showthread.php?p=31373004&posted=1#post31373004 in general hardware about building a rig for video editing (premiere, After effects, etc.)

I have 3 monitors so we were thinking dual GPUs, 450 GTSs to be exact, since these have CUDA functionality but don't need to be top of the line gaming since I will be doing zero gaming on this computer.

We were wondering, does a second GPU in any way contribute to performance via CUDA or any other way in the video editing/rendering process?

CUDA can leverage multiple cards. At least with pro cards. Probably depends on whether or not there's driver support. Try and find an SLI review where they used badaboom and see if it scaled. I'll have a look around and see. It's a good question.

 

[UpstartXT]

I have been doing some research on this. It seems as though it is definitely possible to have CUDA enabled on multiple GPUs at the same time. So from a hardware and driver standpoint, the answer is yes.

However, whether or not there will actually be a performance gain is dependent on whatever program you are using and whether it properly distributes tasks to both GPUs or just loads up one and leaves the other idle.

Or so I think that's what I read lol

So now I am trying to find specific info about the programs I want to be using (Premiere, AE, primarily).

 

[3DVagabond]

Just had a look at HardwareHeaven, they do some GPU compute benches. When they review nVidia cards, even SLI reviews, they only use one card for the GPGPU benches. Not definitive, but not a good sign.

 

[UpstartXT]

Yeah, I also am having to infer the answer.

http://www.studio1productions.com/Articles/PremiereCS5.htm

If you go down to the chart with all the CUDA supported graphics cards, then look at the GTX 295, which is essentially two GPUs put into one card, you will notice in the notes section that while the card has 480 CUDA processors, it is actually "(240 per GPU) Premiere CS5 at this time only supports 1 GPU"

I guess that means no?

Assuming the second card has no effect on CUDA performance, any idea on what option I should go with specifically in my case?

I have a couple of 8800 GTSs lying around, so I was thinking I would by one GTS 450 to be my CUDA card and put two of my displays on that, and then pop in the 8800 GTS as the second card and put my third and fourth display on that?

Or will that not work due to different drivers between the two?

 

[3DVagabond]

Well, according to nVida's SLI support page they do support multi GPU GPGPU with GeForce cards. (Imagine finding it right where it should be) I only happened upon it checking out something else.

GeForce based graphics cards are supported in single, 2-way, 3-way, and 4-way multi-GPU configurations, depending on the specific product. This support encompasses both SLI graphics rendering and multi-GPU general purpose computing.

For more information on the Geforce family of consumer graphics products, click here: GeForce Product Family

For system configurations with more than 4 GPUs, NVIDIA recommends Quadro or Tesla solutions.

http://nvidia.custhelp.com/cgi-bin/...SZwX3NlYXJjaF90ZXh0PVNMSQ!!&p_li=&p_topview=1

 

[UpstartXT]

Well, according to nVida's SLI support page they do support multi GPU GPGPU with GeForce cards. (Imagine finding it right where it should be) I only happened upon it checking out something else.



http://nvidia.custhelp.com/cgi-bin/...SZwX3NlYXJjaF90ZXh0PVNMSQ!!&p_li=&p_topview=1

I'm not so sure exactly what this is saying, there are several interpretations:

-You can have multiple GPUs, and still be able to use CUDA on one of the GPUs

-You can have SLI'd GPUs, and still be able to use CUDA

-You can have multiple GPUs and they will stack CUDA processing power so the more you have the more power you have

Now, from what I have read, interpretation 1 is certainly true no question. Interpretation two is true, but I have read that the CUDA processing power is limited to that of the lowest performing card and is limited to the one GPU. Interpretation 3 as far as I can tell is technically true, but CS5 is not coded properly to be able to benefit from multiple GPUs. This is kind of like when quad cores came out but no video games were coded to utilize them.

 

[aka1nas]

I played around with CUDA for a bit around 2008-2009 or so when I was picking my thesis topic, and at the time CUDA was completely unaware of SLI but could address multiple GPUs. The developer would have to target them manually and deal with load balancing and memory management, etc.

This may have changed in the meanwhile, so take that with a grain of salt.

 

[3DVagabond]

Well, I read that as CUDA will definitely scale across multiple GPU. As you say, CS5 might not have the support though. If that's the case, get the most powerful GPU you can afford.

 

[notty22]

This opencl benchmark ratgpu , http://www.xnormal.net/ratGPU/
That I've run on my SLI rig, definitely uses both gpu's.
And it uses them whether I have SLI selected in NV control panel or not. You easily switch in and out of SLI.
My point is, it just depends on the program is coded, how it may take advantage of installed gpu's.
Though to be cautious, you might want to get a gpu with more cores, like a gtx 460 VS 2 -gtx 450's . For the programs that 'see' only 1 gpu.
edit: I see now, to use 3 monitors, the 2-450's works.

 

[UpstartXT]

Yeah so then if you are using CS5 and are trying to decide on a GPU, use this http://www.studio1productions.com/Articles/PremiereCS5.htm

CS5 apparently is not coded to take advantage of multi GPGPUs.

Looking at that chart, what do people think is the best buy?

 

[1h4x4s3x]

*whisper*
I'd love if someone could do a extended Mercury Playback Engine review with various GPUs/CPUs to compare image quality, speed etc.

 

[UpstartXT]

I dunno, anything but the 450 is really just out of my price range. Think I'm going to get two of those (need second one for multi-monitor even though it seems it won't help with CS5).

 

[3DVagabond]

Yeah so then if you are using CS5 and are trying to decide on a GPU, use this http://www.studio1productions.com/Articles/PremiereCS5.htm

CS5 apparently is not coded to take advantage of multi GPGPUs.

Looking at that chart, what do people think is the best buy?

Well, the GTS-450 has 1gig ddr5. It meets the criteria. I understand you need 2 cards to drive 3 monitors. If you don't need surround, which it doesn't appear you do, you might consider 2 different cards. One smaller one, just to drive 1 (or 2) monitor(s) and a second larger card, more CUDA cores, to actually do the MPE work. Although I'm not sure it would be worth it. What's your budget?

 

[UpstartXT]

I would say about $300-$400 total for two cards.

I do have an 8800 GTS I could use as the second card just to drive the monitors, and buy maybe a better card to do the MPE work.

I'm also not up to date on how it works if you have two different cards, how you install the drivers and all of that?