PhysX When SLI on Single

[Kaguya]

I have a pair of GTX 260s in SLI and with PhysX enabled in the drivers (186.18), and an SLI profile of Single, will one card do graphics and the other do physics, or will one card do both graphics and physics while the other sits idle?

[john19055]

The GTX 260 will do PhysX buy itself,IMO it always good just to leave it in sli and enable PhysX in the control pannel.Sure you could take you SLI bridge off and run one card normal and use the other GTX 260 just for PhysX,But IMO that would be just a waste of your card.Because you are going to see a big improvement running SLI with PhysX just enable,in probbaly 98% of your games.I would use the newest drivers to make sure you have the newest PhysX drivers.

[ChrisRay]

If you have PhysX enabled and SLI off. The second GPU will allocate itself to purely physx processing. I know its not well documented. But this is the case.

Chris

[Kaguya]

Originally Posted by ChrisRay

If you have PhysX enabled and SLI off. The second GPU will allocate itself to purely physx processing. I know its not well documented. But this is the case.

Chris

But I would have to actually disable SLI in the control panel for this to occur? Okay - I don't have intentions of running like this, but just wondered for games that don't properly support SLI but do have PhysX (only one that I know of, but whatever) that if I ran in Single GPU mode with SLI on, which card was doing physics. Thanks!

[AdamK47]

I'd like to know as well.

[ChrisRay]

Yes SLI has to be disabled in the control panel. Otherwise a "Single GPU" profile will run PhysX off the primary card as well.

[FearMeAll]

Originally Posted by ChrisRay

Yes SLI has to be disabled in the control panel. Otherwise a "Single GPU" profile will run PhysX off the primary card as well.

that's dumb. They need to change that badly.

[ChrisRay]

Due to the way the profiling system works. It cannot be changed. Enabling "SLI" is a driver flag that tells it how to percieve the other GPU. IE is it a render device or a secondary monitor/PhysX device. Its important to note that pretty much any PhysX title to date has an SLI rendering profile. And its highly unlikely future titles will ship with no multi GPU support.

It's not a question of being "Dumb". The drivers do this to make SLI profiling work as seemlessly as it does. If you want dedicated PhysX. You wouldnt want SLI enabled in the first place.

[FearMeAll]

Originally Posted by ChrisRay

Due to the way the profiling system works. It cannot be changed. Enabling "SLI" is a driver flag that tells it how to percieve the other GPU. IE is it a render device or a secondary monitor/PhysX device. Its important to note that pretty much any PhysX title to date has an SLI rendering profile. And its highly unlikely future titles will ship with no multi GPU support.

It's not a question of being "Dumb". The drivers do this to make SLI profiling work as seemlessly as it does. If you want dedicated PhysX. You wouldnt want SLI enabled in the first place.

I'm just mad that Sli in Batman with physx is so much slower than single card with physx. It doesn't make sense. 2 gtx280s should kick Batman's ass physx and all.

[ChrisRay]

Originally Posted by slaWter

But how does it work if you have a GTX 285 SLI plus a 9800GT for example? Is is possible to define the 9800 GT as a dedicated PhysX card and still use both 285s for SLI?

Will there be a drop down menu (like with the SLI focus display) in the NVCP in this case?

Yes there will be. But I wouldn't recommend this setup. You wont see much if any performance gain.

[kuddles]

So if a game like Batman or Mirror's Edge has hardware PhysX, it actually runs better if you turn SLI off? I guess that kinda makes sense - each individual card doing their own task instead of both of them performing the same two tasks at the same time.

I'm guessing this won't work on my GTX 295, though, since the 2nd GPU would have to be on a separate slot to be dedicated to PhysX.

[ChrisRay]

Originally Posted by kuddles

So if a game like Batman or Mirror's Edge has hardware PhysX, it actually runs better if you turn SLI off? I guess that kinda makes sense - each individual card doing their own task instead of both of them performing the same two tasks at the same time.

I'm guessing this won't work on my GTX 295, though, since the 2nd GPU would have to be on a separate slot to be dedicated to PhysX.

Not neccasarily. It depends on game, Resolution, and rendering bottlenecks. Dedicated PhysX cards are mostly useful in my experience ((compared to standard SLI renderings)) at lower resolutions where PhysX processing is the primary bottleneck. But range can vary widely depending on settings and such.