Multiple GPUs and CUDA

Paul Masters wrote on 1/12/2011, 3:32 PM
I am building a new i7 970 system with 2 monitors and agonizing over which video card to get.

I can get 2 EVGA GTX 460s for about the same price as 1 EVGA GTX 570. They both are super clocked and have about the same spec.
Except: cores - 336 vs 480. Memory - 1GB vs 1280 MB. Memory interface - 256 vs 320 bit.

I have read some threads here and as one should expect, the results say ‘your milage may vary’. (Currently have a 9800 GX2 which has CUDA.)

I have asked a question on the NVIDIA forum but have received mixed response as well. Part of the problem is, I think, that they are gamers and I am not. Another part is that the modern video cards are designed more in the direction of gaming while video editing doesn’t use the modeling, texturing, etc. that games do. Video editing and display need encode/decode processing. (I see that some new Intel CPUs are out which contain video encode/decode processing in the chip. However, as Vegas / DVD Architect doesn’t use that yet and the higher level CPUs are not yet available I am ignoring them at this time. May be in 1 or 2 years.)

As I don’t understand how CUDA works or how Vegas uses it I have the following questions that I hope someone can answer or at least confuse me at a higher level.

Will Vegas use the processing in 2 cards if they are not connected (SLI bridge)?
Will Vegas use the processing in 2 cards if they are SLI bridged - that is, does Vegas use SLI?

As CUDA is a method to use multiple processors, I would guess that the more the better?

Does Vegas / DVD Architect use any other feature (PhysX etc.) for display or rendering/encoding? (I doubt it, but then “I know nothing...nothing”.

Any thoughts on which card would be best with Vegas?

Thanks for any comments.

Paul Masters

Comments

john_dennis wrote on 1/12/2011, 4:07 PM
From a previous post...

With a Q9450 on WIndows 7 (64 bit) and Vegas Pro 10.0 (64 bit), I got about a 20% bump with the Sony AVC codec over Vegas Pro 9.0e (64 bit) with an nVidea GTS450. The card will cost me $60 when the rebate comes back. I was ready for a new card to replace the 7600GS. The new one has HDMI. Overall, it was worth $60 to me, especially since the timeline playback is a little smoother.

These are measured results. The details are in this thread:

www.sonycreativesoftware.com/forums/ShowMessage.asp?ForumID=4&MessageID=744247

There have been reports of less improvement with much faster system processors. Don't know about SLI. Frequently, there are diminishing returns in managing the distribution of work to lots of cores. Perhaps, we need a "RenderTest 2011 for AVC with CUDA". I usually just take a fixed length of AVCHD video and watch the clock while it renders.
John_Cline wrote on 1/12/2011, 4:38 PM
Both the earlier and current versions of my "Rendertest" really stress the CPU and wouldn't be a good benchmark for testing the speed of Cuda compression. The computer would spend much more time rendering than encoding. Let me see what I can come up with that puts as little stress on the CPU as possible and as much as possible on the Cuda GPU.
JohnnyRoy wrote on 1/13/2011, 6:42 AM
> As I don’t understand how CUDA works or how Vegas uses it I have the following questions that I hope someone can answer or at least confuse me at a higher level.

This can be answered very simply.

Vegas Pro 10 uses the GPU for rendering to the Sony AVC format. That it!

There is no other use of the GPU in Vegas Pro 10 or DVD Architect 5.2. Having a massive CUDA card will not improve playback or anything else at all; just Sony AVC rendering.

~jr
DavidMcKnight wrote on 1/13/2011, 2:07 PM
john_dennis said: "...with an nVidea GTS450. The card will cost me $60 when the rebate comes back. "

John, is that rebate / deal still in effect?
john_dennis wrote on 1/13/2011, 7:06 PM
The deal that I found was during the holidays at Frys, Northern California. You could check Frys.com but the sales vary. Currently, they have a Galaxy GTX460 for $139.99. YMMV