I've been long trying to get both GPUs on my GTX295 to run simultaneously but not much of a success. I've tried BOINC 6.6.25 with SLI and PhysX off. BOINC detects both of my GPUs but said in the message tab, CUDA device (not used) GTX295.... Is there any setting that I have to put on to use second GPU?

I've put a command line <use_all_gpus>1</use_all_gpus> in BOINC's cc_config file but it still use only 1 GPU.

I've been long trying to get both GPUs on my GTX295 to run simultaneously but not much of a success. I've tried BOINC 6.6.25 with SLI and PhysX off. BOINC detects both of my GPUs but said in the message tab, CUDA device (not used) GTX295.... Is there any setting that I have to put on to use second GPU?

I've put a command line <use_all_gpus>1</use_all_gpus> in BOINC's cc_config file but it still use only 1 GPU.

It sounds like you offering up a GTX295 ... I only have one, I'll take another :-)

Thought I would just lightenthings up a bit :-)

Steve

OK ... on a more serious note, I have found that whenever I mess with almost anything in regards to my GTX295 (new driver, new boinc, changing SLI and/ or PhysX settings) I typically need to reboot at least once if not twice to get boinc to recognize that the 295 actually has two cores. I almost always get compute errors even though I stop boinc and tell it to unload science. I think next time I will try stopping boinc, unload, reboot, make my changes, reboot, reboot, restart boinc ... it also does not seem to like suspension either as that seems to cause compute errors also. I have not actively tried to reproduce any of these scenarios but it sure seems like whenever I mess with things, they mess with me back. I guess the lesson for me is to leave it alone and let it crunch!!!

Steve

OK ... on a more serious note, I have found that whenever I mess with almost anything in regards to my GTX295 (new driver, new boinc, changing SLI and/ or PhysX settings) I typically need to reboot at least once if not twice to get boinc to recognize that the 295 actually has two cores. I almost always get compute errors even though I stop boinc and tell it to unload science. I think next time I will try stopping boinc, unload, reboot, make my changes, reboot, reboot, restart boinc ... it also does not seem to like suspension either as that seems to cause compute errors also. I have not actively tried to reproduce any of these scenarios but it sure seems like whenever I mess with things, they mess with me back. I guess the lesson for me is to leave it alone and let it crunch!!!

Steve

Did you put it in the options section?
Stop and restart BOINC?

Because It works for me with my two GTX295 cards and 6.6.25 and 6.6.26 ...

PM me if you want and I will send you mine ...

SLI needs to be off. PhysX needs to be on.

Turning PhysX off will disable 1 GPU in my experience.

Failing that Dummy VGA plug required or add LimitVideoPresentSources DWORD 1 in the registry. See other 295 posts for full description.
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( VC means VideoCard )
And another issue many seem to forget check with a program like systeminfo,everest or sisoft sandra what irq's are being used.
find the VC on the list and see if it is shared with other devices.
Because on most occassions it can be that the windows/bios has put another device on this irq
Now it depends on this device if it can become a problem because their are power device (masters)and weak devices (slaves)
Now when you see another device on the same irq with the irq of the vc like a usb controller or pci bridge then it is ok those are slaves.
But if you see a network, harddrive or audio device on it you have a problem to solve, the masters will allways interfere with another master.
There are some tricks to solve this like for instance go into your bios and disable devices which you probably don't use ( com, lpt or gameports) or even raid controllers.
Now some people think windows should do this or the mainboard and yes your right it should do it, but believe me it many cases it does not.
If that does not help sometimes a reset of the bios settings to defaults does help.