2 or more graphics cards on the same mainboard

Accelerated Computing CUDA CUDA Programming and Performance
#1

If I put two or more say 8800 GTX graphics cards on the same mainboard, can I call them individually through the API? So can I send one task to card 1 and another task to card 2 etc…?

What happens if I put 2 cards in SLI? Will the API see 1 card with twice the ALUs and twice the memory?

Thanks

#2

And if CUDA supports SLI indeed, how scalable is this configuration?
I guess, it could not be ideally linear. :blond:

#3

Yes, you can explicitly create a CUDA context on each GPU in the system to address them separately. CUDA does not support “SLI” in the graphics sense – that wouldn’t make sense.

If your application is highly parallel and can be divided into blocks that have no dependencies (and is not bottlenecked by PCI-express transfers), then using multiple GPUs can provide very good scaling.

Mark

#4

Thanks for your reply Mark. This is indeed the case with my applications so this technology might be potentially very powerful.

#5

As far as I understand, the global functions are called synchronously, and each this function can be called only on one device at the same time. So, do you mean that those “parallel” calls should be done by different CPU threads or maybe processes?

-Ivan

#6

Yes, exactly. We recommend creating one CPU thread per Quadro GPU. In each thread, create a CUDA context (the CUDA runtime API enables you to enumerate the GPUs and choose one to create the context on).

Mark

#7

Mark,

Can I use runtime api, not the driver api to create a context?

I’m working in a cpu multithread environemnt and need switch the same context between multi-threads. I see the example to do this using driver API, can I do same thing using runtime API?

thanks.

mayt

#8

Another question, can I mix runtime API and driver API in one application?

Thanks.

#9

According to various posts from nvidia individuals on that forum, this is not allowed and will result in troubles.

Cédric

#10

I think that’s not allowed with the runtime api. But you can use the GPUWorker class posted on these forums to deligate work to worker threads from a different thread. I’m not sure if you can have multiple threads submit work to the GPUWorker, but you could perhaps modify it to allow that.

#11

Thank you, I think that works for my case.