My setup:

2 - 8800GT running the latest Nvidia drivers

One video card is set for video, the other is set for Phys-x

under this config I can run 2 instances of SETI@Home ( CUDA ) and both cards will max out the CUDA processers and the math will fly. Takes about 5 mins to process each SETI@Home work load.

But, if I take the same setup, and do nothing but turn on SLI mode, the 2 instances of SETI@Home ( CUDA ) basically crawl and the video cards seem to just idle. Takes over an hour to process each SETI@Home work load.

As well, if I leave the setup in SLI mode, BUT only run one (1) SETI@Home ( CUDA ) process, it flys again and takes 5 mins.

Any comments?

IIRC SLI is known not to play nice with S@H.

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SETI@home classic workunits: 93,865 CPU time: 863,447 hours
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IIRC SLI is known not to play nice with S@H.

And also IIRC, SLI was decoupled from the drivers many, many driver versions ago.

In theory, at least. It would be worth investigating the "two instances, SLI enabled" case in more detail, to ensure that BOINC is correctly identifying both graphics cards and assigning the tasks appropriately.

And everybody asking a question - please don't just say "the latest" of anything. I know it doesn't take us long to click through and see driver 280.26 under 64-bit Windows 7, but it always helps to have all the information gathered together in one place before we start.

Welcome (with your first message here) in the S@h forum.

SLI need to be disabled during S@h CUDA calculation.
Normally newer drivers should disable it automatically.


- Best regards! - Sutaru Tsureku, team seti.international founder. - Optimize your PC for higher RAC. - SETI@home needs your help. -

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Thanks All.

When I installed 280.26 under 64-bit Windows 7 ( sorry, my bad for not saying before ) it defaulted to have one card video and one card phys-x. I then turned on SLI via the Nvidia software and tested out some games. All was well, with high frame rates etc. as expected. But when I left it in SLI mode and tried S@H that's when things got wonkie.

The Bionic Manager shows both CUDA tasks running, each assigned to a different video card, but performance was horrid. Went in the Nvidia software, turned off SLI, then things are great for CUDA.

I'm not going to worry about it, I was just wondering if there was an easy explaination. If it's just a case of S@H and SLI not playing well... then that's good enough for me.

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