Sorry, but I'm not sure that I've found an answer to this one....IIRC, it's No...., but:

Does PhysX have any benefit strictly for crunching?

Thanx!

PhysX is CUDA-powered now. So it's just another CUDA application using your GPU like GPUGrid.net and the SETI CUDA client.

Ok, Thanx, it's turned off, but I wanted to try to get some kind of straight answer....

Thanx!

I have to have PhysX turned on for the 6.5.0 client to see my second card and I have not noticed any drop in performance and no issues at all.

Pat

Well if you don't use Physx it does not use anything nor screws up running gpugrid, so it does not matter if it is turned on or off.
But if a Physx process gets started it will mess up the gpugrid calculation.
Although if you look at the nvidia panel the physx demo clearly runs without crashing gpugrid so maybe it is related to the use of memory on the card.
A friend of me had a big physx process running and the unit from gpugrid error out, so now he closes boinc when doing these physx processes.

but I wanted to try to get some kind of straight answer....

Was his answer (or the following ones) not straight enough?

MrS

For me it has to be enabled or I loose 1 GPU for crunching.
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For me it has to be enabled or I loose 1 GPU for crunching.

Again Physx is only used in some games or applications so it won't mess with the boinc projects as long as you not game or run these apps together with boinc at the same time.
I would not want to game if boinc is running (me wants speed then ;))
So just leave the physx turned on the only thing what messes up is sli which only makes you see 1 card instead of 2 which in fact is what it should do :)
If you don't have another card you can leave that as is also ;)

Indeed. this has happened since drivers 181.xx and with BOINC's from 6.6.15.
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I just went through a harrowing couple of hours...I decided to update the driver on my windows box:

XP64
6.5.0
9800GX2
181.22 driver

After the upgrade to 185.85 (I am back to 181.22), I 'lost' a gpu. Only 1 wu would crunch. I finally remembered about PhysX...Some how, my mode changed to 'Enable multi-gpu use' (this must be the Ntune software SLI switch..?) and 'PhysX Enable'. After trying the finite combinations, and dumping the 'in process' wu, I got this:

I had to Disable PhysX and Disable 'Multi-GPU mode', to get the 2nd GPU to run.
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Consciousness: That annoying time between naps......

Experience is a wonderful thing: it enables you to recognize a mistake every time you repeat it.