2 GTX295 Quad Sli plus GTX 285 for physx

Flanno · 24 Sep 2009 at 13:02

Am currently running 2 GTX295's in quad sli. My brother has offered me his GTX285 for free as he is going ATI soon. Would it be possible to use this for just Physx ? So is quad sli plus physx possible ?

Calneon · 24 Sep 2009 at 14:34

Flanno said:
Am currently running 2 GTX295's in quad sli. My brother has offered me his GTX285 for free as he is going ATI soon. Would it be possible to use this for just Physx ? So is quad sli plus physx possible ?

Aren't you happy enough with the performance of 2x GTX295s?

What current game would benefit having 2x GTX295s and a GTX285?

Theguy · 24 Sep 2009 at 14:39

Thats not what Flanno is asking though is it.. god no's what the elecy bill would be. but the op is asking if physicx would work, personally i would say probs yes. but, i guess theres only 1 way of finding out, particularity if its free. if its not working you could always jsut give it back couldnt you.

vertica · 24 Sep 2009 at 14:40

It is certainly possible and will work, but its a waste of all that power! Will generate even more heat, require two more pci-e power connectors etc etc

If you go by 3dmark vantage, then offloading the physx to a dedicated card will net you about 1.5k-2.5k points more (from experience in 'P' mode). But in realworld gaming situation it will be negligable.

You'd be better off selling the 285, and if you were still keen on adding another card for physx, buy a 9800gt "eco/green" and keep the profit!

The physx processing will be almost identical, but with much less heat, no additional power cables to the card etc.

Antx777 · 24 Sep 2009 at 15:03

What PSU are you currently using to run the GTX295's?, as an added 285+ those two = a lot of power (probably 1KW+ required?)

Rroff · 24 Sep 2009 at 15:03

I doubt you'd see a difference with QUAD SLI unless you were using a hydra multi-GPU board... 4 card scaling with SLI is inefficent enough that you have masses of headroom physx can use without impacting directly on rendering performance...

Flanno · 24 Sep 2009 at 15:04

Thanks for the advice lads. I'll give it a go to see if it works anyway. I assume more decent games run physx now. Last time I looked, twas when Aegia were trying to make a go of it.

By the way, I assume the Corsair HX1000w will be up to the job. Running a 920 @ 4ghz, Corsair H50, 2 velocirpators and a 2tb wd green for storage.

Flanno · 24 Sep 2009 at 15:08

Rroff said:
I doubt you'd see a difference with QUAD SLI unless you were using a hydra multi-GPU board... 4 card scaling with SLI is inefficent enough that you have masses of headroom physx can use without impacting directly on rendering performance...

I thought on X58 mainstream boards and mainstream Nvidia cards, you had to dedicate a card for physx directly or else it would just use the cpu. So even if there is headroom left over with Quad SLI, physx wont work on either card unless I just use 1 295 for gaming and assign the other to physx. Which wastes a 295.

I'm also thinking that all X58 mobos that don't have the NF200 chips or chips, will be limited to 32x lanes. So I'll end up with 16x for 1st 295, 8x and 8x for 2nd 295 and whatever I use for physx. Would I see any performance drop in games that don't use physx then, given I currently run at 16x,16x for both 295's, or has the 2nd pci-e slot not been saturated beyond 8x for current games anyway ?

vertica · 24 Sep 2009 at 15:10

1KW will be pushing it. Under full load with a OC'd system like yours i'd think you would be pushing 900W at the wall at the moment.

I've based that on my setup, which @4Ghz and a single 295 (albeit OC'd quite a bit) pulls 650W under furmark and prime.

Add another 295 and a 285 and i dont think 1kw would cut it for very long. (even including the 80% effeciency) Also does the PSU have sufficent current capacity ont he 12V rails?

vertica · 24 Sep 2009 at 15:16

Flanno said:
you had to dedicate a card for physx directly or else it would just use the cpu. So even if there is headroom left over with Quad SLI, physx wont work on either card unless I just use 1 295 for gaming and assign the other to physx. Which wastes a 295.

Not true, in the same place you enable SLI in the NV control panel, there is a "use physx" radio button. If its on yes then the physx is done on card, no need to get rid of the SLI, The drivers cope with that side of things, allocating the physX/CUDA calcs and the graphics processing as required to each of the four gpu cores.

Rroff · 24 Sep 2009 at 15:18

Flanno said:
I thought on X58 mainstream boards and mainstream Nvidia cards, you had to dedicate a card for physx directly or else it would just use the cpu. So even if there is headroom left over with Quad SLI, physx wont work on either card unless I just use 1 295 for gaming and assign the other to physx. Which wastes a 295.

I'm also thinking that all X58 mobos that don't have the NF200 chips or chips, will be limited to 32x lanes. So I'll end up with 16x for 1st 295, 8x and 8x for 2nd 295 and whatever I use for physx. Would I see any performance drop in games that don't use physx then, given I currently run at 16x,16x for both 295's, or has the 2nd pci-e slot not been saturated beyond 8x for current games anyway ?

I'm using 260GTX SLI and in SLI mode I don't have to dedicated a card to physx and it deffinatly runs hardware accelerated - what I don't know is if it uses 1 of the 2 cards or load balances physx over both in SLI mode.

Aslong as they are x8 PCI-e 2.0 then you shouldn't really see much difference...

bare in mind the NF200 chip usually has x16 lanes into it and then splits that to 2 lots of x16 lanes out... and switches... so its not like having true dual x16 lanes - but for SLI/multi GPU it works great as the NF200 chip can upload data to both cards at the same time and shortcut transactions between the cards... which in theory means you get better gains than normal with SLI tho from my testing it looks like only 5-10% better tops.

DavyBoy · 24 Sep 2009 at 15:19

LoL, a GTX285 for PhysX?!?!

That would be completely pointless and a total waste of electricity..

The 4 GPU's on the 295's will have more than enough processing power to deal with PhysX..

It could easily be done though, but I really dont understand why you would want to do it???

I am only using a single GTX280, and it copes perfectly fine with PhysX games.

And as for dedicating a card for PhysX, yes this can be done in the Control Panel if you had a card that you wanted to use solely for PhysX, but if it is just set to enabled the work will be done by your main GPU(s) instead.

Flanno · 24 Sep 2009 at 15:48

Thanks again lads. Didn't realise in the control panel you could enable physx and it work on the main gpu's.

As for why I'd want to do it. Cause the card is free and I don't want to sell it

But I take everyones point on heat, electricity and the 1kw psu maybe being tight.

Flanno · 24 Sep 2009 at 15:51

Rroff said:
bare in mind the NF200 chip usually has x16 lanes into it and then splits that to 2 lots of x16 lanes out... and switches... so its not like having true dual x16 lanes - but for SLI/multi GPU it works great as the NF200 chip can upload data to both cards at the same time and shortcut transactions between the cards... which in theory means you get better gains than normal with SLI tho from my testing it looks like only 5-10% better tops.

yeah..I was looking at the asus supercomputer board which has dual NF200 chips opposed to the one on the EVGA classified. Too expensive though.

HazardO · 24 Sep 2009 at 15:54

I wouldn't have thought you would be able to use the GTX285 as your physx card while you've got 2 GTX295s. The drivers aren't written to cope with 5 GPUs.

Flanno · 24 Sep 2009 at 16:02

I was thinking of that also. This supercomputer board from asus is able to support 4 4870x2's in 16x mode. It has 64 lanes. Though I'm not sure the drivers will handle it.

Sayso · 24 Sep 2009 at 16:20

overkill tbh...but you e-peen will be king dong length

LoadsaMoney · 24 Sep 2009 at 16:24

It wont work will it, as that would be 5 GPU's.

HornyRhino · 25 Sep 2009 at 01:56

the question of whether you can have a quad sli and a physix has been tested and restested in many other forums....Answer..you can but you really wouldnt notice it with quad sli

.

apparently the drivers are written to only cope with upto 4 gpus in sli running the actual graphics but the physix is an extra element done via cpu/sli gpus/extra card

loads of info via Gods Magical Landline 'Google'

example...http://www.evga.com/forums/tm.asp?m=100871055

Regards,

HRhino"