Quad SLi PhysX question..

Syncroneyes · August 12th, 2008, 06:52 PM

Ok so i've downloaded all the new 177.83 drivers + updated Physx software pack and installed it all and its working pretty good with my 2 x 9800GX2 cards enabled in Sli.

But what I wanna know is it possible to have it setup where SLi is disabled and: 1 x GX2 card = 3D
& 1 x GX2 card = PhysX

I can't seem to access the tab in PhysX settings to choose which GPU runs the physx..

-Is it even possible to do this using two GX2 cards? or does 1 x GX2 card = an SLi configuration so its not recognised or something?

I'm using Vista 64 and I know about the workaround to extend ur desktop to an additional monitor. I tried that but couldnt get it to work (i used one monitor and connected two cables to either GPU then extended my desktop but it didnt work, afterwards I still couldn't enable the tab to choose which GPU for Physx.

So, like, is it even possible or am I just wasting my time?...

Unixlord · August 12th, 2008, 07:17 PM

You want to devote one entire 9800GX2 gpu to physics? Are you insane? That's such a waste even if it was possible.

Syncroneyes · August 12th, 2008, 08:55 PM

LoL don't worry, its not for all games

Just for the Physx intensive games like UT3 and GRAW2 - for these games a single GX2 will run the graphics just fine, which means i could then dedicate the other card to doing the physics and thus get optimum framerates.
(as i said, at the mo Quad Sli is working pretty good with PhysX, but it could be a lot better -i'd like to have a dedicated PPU when i need it)

Unixlord · August 12th, 2008, 10:31 PM

Well I can't find any info on using a gpu as a dedicated ppu and certainly not a 9800GX2 which would be adding another layer of complexity.
We have a saying here: "Just because you have rope doesn't mean you have to hang yourself with it".

Syncroneyes · August 13th, 2008, 03:16 PM

hehe thats true, I think I have found a solution now though:

I have kept both GX2 cards in SLi whilst also selecting Geforce PhysX. Then in Nvidia control panel I have selected "3 GPU Alternate frame rendering".

This I believe will use 3 out of the 4 GPUs for running 3d graphics and then use the 4th GPU only to calculate the PhysX. So far it seems to be working well. I have only tested for short time with GRAW2 and I need more time to test & confirm but so far so good.

Before in quad SLi with default "Nvidia recommended" SLi setting I could only play with decent framerates using "PhysX High" setting in GRAW2. Now using 3 GPU Alternate frame rendering I can play with the "PhysX Extreme" setting and still get pretty good framerates.

GRAW2 now looks even more gorgeous and runs quite smoothly, I never thought I'd admit this but PhysX has changed this game so much for the better and adds a whole new layer/dimension to the gameplay: tyres explode rocking the car bodies they way they should, explosions feel more heavy and also have more particles, trees gently sway in the wind...plus there's much more.

Stand by for further testing & confirmation but, dare I say it, this PhysX sh*t actually works!

Syncroneyes · September 5th, 2008, 04:24 PM

After further testing I've decided that even though the PhysX effects are really cool and they do add more depth to games, overall I think, the way it is at the moment, enabling Geforce Physx still reduces the FPS too much when gaming. - even for high-end SLI systems.

Nvidia really need to look at improving the PhysX performance considerably with their upcoming driver combinations if they want it to succeed..