I was fortunate to recently acquire two EVGA GTX680 video cards with the same exact manufacturers part number (02G-P4-2682-KR) and I wanted to put these cards in SLI mode. I ran each card by itself to determine how well the cards would process GPUGRID work units. At no time where the cards overclocked nor any adjustment made to any card settings. Both cards ran fine.

Now the problems starts.

When I installed the second card the BOINC application did not run another work unit for the additional card. The cards were properly installed, Windows did recognize both cards and had no other exceptions were noted. I attempted to run the same configuration under Ubuntu 12.04 and found that BOINC would not download any GPUGRID work units as the event log message stated "No GPU. No CUDA cores could be found..." (may not be the exact language, but very close). I checked the NVIDIA settings and found the Memory clock for one card was 3004 Mhz and the other card was 3104 Mhz. Could this difference be the issue why these two cards will not function together? Individually in non-SLI mode each card runs fine and work units were received and processed without any problems. I later installed the cards in another computer in SLI mode to ensure it was not an issue with the original computer. Same result occurred.

Any ideas?

Thank you.

This doesn't answer all of your question, but it appears using SLI mode gives errors in general, and isn't recommended. If you look through some of the older forum posts you can see that SLI should be turned off when crunching.

You have to tell Boinc to use both GPU's.
To do this create, or edit if you're already using, a cc_config.xml file, with the following line,
<use_all_gpus>1</use_all_gpus>

See the FAQ - Best configurations for GPUGRID thread about creating a cc_config file.

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I had tried with SLI enabled on Win7 and it seemed to work, as long as you completely shut down BOINC before switching to/from SLI mode.

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I will try both suggestions during the next couple of days and report back. Thank you for your input, it is appreciated.

Ray

werdwerdus.
I followed up with you suggestion and I reinstalled the video card. Upon installation I found the NVIDIA settings had disabled the SLI mode and after I enabled "SLI mode" and rebooted the computer the software showed both video cards with the approximately the same voltage and GPU clock numbers. Before one card was operating at approximately 1/3 the numbers of the other.


skgiven,
The BOINC software I am using for whatever the reason did not have a "cc_config file" present in the BOINC directory. I did not think that was possible, but it was. I added this missing file and included your coding and now both cards are crunching away.


Thank you very much to both of you for your kind assistance. Without your help, this would have been a very frustrating exercise.

The cc_config.xml file is only present in the Linux version of Boinc. While it's not actually configured; it just lists the commands, at least it's there to edit.

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Hi all, how to enable two tasks in gpugrid on sli nvidia 680gtx in windows 8 ? In which folders i have put cc_config.xml file? lokal disk-program files-BOINC...im create one cc file in notepad and put there,turn off boinc aplication ,but nothing happened. sli is enabled in nvidia panel" only one task in boinc manager running now..

Create the cc_config file in the ProgramData\BOINC folder.
It's probably C:\ProgramData\BOINC\
This is most likely a hidden folder but you should be able to enter the location directly into Explorer or from Start (if you can find them in W8).

<cc_config>
<options>
<use_all_gpus>1</use_all_gpus>
</options>
</cc_config>

Remember to save it as a .xml file!
So when using a text editor Save As, choose All file types and call it cc_config.xml

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Uff..some kind of fight with windows 8 search Explorer-)) .. The problem was- the need to place in the search, in the win 8 search expl.---C:\ProgramData\BOINC without \ on the end -))
Now everything work great!
Thank you very much skgiven.
And for all,skol