I've tried doing this over the past week with no success. I am running 2x GTX 295, 1x 9800GX2 on a single machine with SLI and physx disabled and still can only get gpu 1 to work. Help is appreciated.

bump for help :)

Do you use a cc_config.xml file in your BOINC data directory?

<use_all_gpus>1</use_all_gpus>

I don't have either of those cards, but have you extended the desktop to them? Does windows "see" them? What does BOINC say in the messages when you start up the client? Does it list only 1 coprocessor?

I have SLI enabled on my 2x 8800GT's and physx on the 1x GT240. That's allowed me to not have to extend the desktop or use any "dummy" connectors, as I've heard others have used.

Maybe someone with these times of cards in a working setup can assist more thoroughly.

If I enable SLI and physx boinc will see 5 gpus 4 295 and 1 9800gx2, but will only fold start tasks for 3 of them. When I try to extend monitors on all cards boinc will only see gpu 0 and gpu 1. I have also tried the config file with no luck.

If I enable SLI and physx boinc will see 5 gpus 4 295 and 1 9800gx2, but will only fold start tasks for 3 of them. When I try to extend monitors on all cards boinc will only see gpu 0 and gpu 1. I have also tried the config file with no luck.

Have you checked if extending the monitor only to all the 295s offers at least some improvement?

Is there an extra connection between one 295 and the next that might allow use of the new 4-way SLI to treat two 295s as just one GPU? Have you checked if use of the usual 2-way SLI in a 295 allows the GPUGRID application to treat the whole 295 as just one GPU, but one about twice as fast?

Have you checked if your CPU is powerful enough to handle the CPU time requirements of interfacing to all the GPUs you have at once?

I've seen some hints that the current software versions might concentrate the effort of driving multiple GPUs on just one CPU core; you might look for signs this has happened.

Also, you might check if enabling only SLI or only physx makes any changes in the results, if you don't want to wait for someone who actually has that set of cards.

If BOINC recognizes only two GPUs, does it mention which GPU types they are?

Also, which BOINC version are you using? I've seen some messages saying that some versions work better with SLI enabled and some work better with it disabled.

Remove your 9800gx2 and use the two GTX 295 cards.
Put the 9800gx2 into another system or sell it.