How much processing power does PhysX use? Is it worth getting a 3rd card to offload PhysX to?

[GuruMeditationError]

I've got two GTX 580s in SLI (water-cooled) and I don't know if I should add a third GTX 580 to offload the PhysX calculations to.

 

I know that adding anything less than a GTX 580 will reduce the SLI to the speed of the slowest card (so I have to add another GTX 580).

 

My question is: does PhysX use enough processing power for it to be worth adding a third card to take the PhysX load off of the second card in my SLI?

 

I'm thinking of adding a third 580 and having it take on some of the processing as well as the PhysX (rather than being just a dedicated physics card) so I'm hoping it should be worth it for the extra speed.

 

What do you guys think?

 

:0) 

[Oshino Shinobu]

Don't do it, it's not worth it at all. PhysX doesn't take that much to run, and not that many games even use it. 

[dragosudeki]

If you are not having trouble with it, don't worry about it.

[Snickerzz]

Don't do it, it's not worth it at all. PhysX doesn't take that much to run, and not that many games even use it. 

this^^

[DoubleY]

God no. If you do, use something like a GTX 660 for Physx

[SparkySamZa]

just tell nvidia control panel to of load it to the cpu simple :3

[M-ursu]

It can make a huge difference in physX intensive games like AC4, but AC4 maybe the only game which shows huge FPS increase, in other physX games you might only get few FPS more, so it is not worth it

[Izaya Orihara]

PhysX doesn't take that much to run

Not exactly correct. Do you know that part in the Metro Last Ligth benchmark when the PhysX stuff kicks in? I get terrible fps there. A deticated PhysX card would stop that.

[Oshino Shinobu]

Not exactly correct. Do you know that part in the Metro Last Ligth benchmark when the PhysX stuff kicks in? I get terrible fps there. A deticated PhysX card would stop that.

Well, in most games it holds true. Still, I don't think there are enough games that really use it to justify another card. I think AC4 uses pretty heavy PhysX too. 

[Izaya Orihara]

I know that adding anything less than a GTX 580 will reduce the SLI to the speed of the slowest card (so I have to add another GTX 580).

This is not correct. You can set  something like a 750 to be a deticated PhysX card. It won't reduce your 580's speed. 

[Buckley]

I wouldn't bother. I mean if you can get like a 560ti for less than $50, yes but even then I wouldnt

[Internet Swag]

Can the load of PhysX actually be too much for the PhysX dedicated GPU? I.E using a 640 for physx

[Morpheus]

just tell nvidia control panel to of load it to the cpu simple :3

Don't do this, it'll take a serious hit to your fps because it's not meant to run on the cpu

[GuruMeditationError]

God no. If you do, use something like a GTX 660 for Physx

 

But wouldn't that just be more expensive? I thought it would be limited to the speed of the 580s? Is that not the case?

 

just tell nvidia control panel to of load it to the cpu simple :3

 

Wow, I did not know I could do that (is that just what happens by default if you disabled PhysX on the cards or do you specifically have to enable it?). Plus I was hoping to keep that load off of my CPU but it seems my graphics cards are probably my biggest bottleneck (or at least their RAM (1.5Gig on each)).

 

 

Don't do this, it'll take a serious hit to your fps because it's not meant to run on the cpu

 

So that's not recommended?

 

This is not correct. You can set  something like a 750 to be a deticated PhysX card. It won't reduce your 580's speed. 

 

So I can fit something with a higher spec. but not a lower spec? I'm not sure if that would work out cost-effective but I suppose it widens the field, in terms of what's available to me, so that might help.

[Izaya Orihara]

But wouldn't that just be more expensive? I thought it would be limited to the speed of the 580s? Is that not the case?

 

 

Wow, I did not know I could do that (is that just what happens by default if you disabled PhysX on the cards or do you specifically have to enable it?). Plus I was hoping to keep that load off of my CPU but it seems my graphics cards are probably my biggest bottleneck (or at least their RAM (1.5Gig on each)).

 

 

 

So that's not recommended?

 

 

So I can fit something with a higher spec. but not a lower spec? I'm not sure if that would work out cost-effective but I suppose it widens the field, in terms of what's available to me, so that might help.

The 580 kills the 750 in raw performance. 

[Izaya Orihara]

Can the load of PhysX actually be too much for the PhysX dedicated GPU? I.E using a 640 for physx

Yeah. I've seen a test with a GTX Titan and a 8800 and it was terrible. 

[GuruMeditationError]

The 580 kills the 750 in raw performance. 

 

Okay, I guess I'm getting confused by the naming conventions. I saw a tech tips video that shows a slower card bottlenecking an sli. It might have been a specific pairing and/or there might be exceptions but I was under the impression that it was a popular misconception that a slower card could be used as a dedicated PhysX card without it slowing down the faster card. To be honest I'm not sure what to believe, since the only real "evidence" I've seen has shown the slower card to limit the faster.

[Fluffinator]

Don't offload physx to CPU that guy probably didn't know what he was talking about. It will work terribly.

[GuruMeditationError]

Don't do this, it'll take a serious hit to your fps because it's not meant to run on the cpu

Don't offload physx to CPU that guy probably didn't know what he was talking about. It will work terribly.

 

Okay, thanks. I wasn't sure since I've got eight cores and am not sure if it could be done in a single core without affecting the other threads.

 

I've been looking at the benchmarks and while at least one game shows terrible scaling with three in sli, a lot of the others show a pretty good increase in performance. My thinking was that I could offload the PhysX plus have the third card taking on a bit of the processing workload. It seems to make sense but everyone seems totally set against it. lol.

 

There's no way I'd go four-way sli but three way is looking pretty tempting. I know it's probably beyond diminished returns but even so, I can get a third card sooner than I can get a single card to outperform the two I already have. :0/

[Fluffinator]

Well, I think you'd be wasting your money because diminishing returns but your call, I think it goes like 75% for 2 way SLU and 50% for third in SLI used of the card.

[GuruMeditationError]

Well, I think you'd be wasting your money because diminishing returns but your call, I think it goes like 75% for 2 way SLU and 50% for third in SLI used of the card.

 

I guess so, plus I wouldn't have to buy more water-cooling stuff if I stick with two. I just don't know how long it's going to be before I upgrade. I guess I have to look at the market to see when the best time to upgrade might be but I think I might be behind the curve already. I was planning on running these into the ground before upgrading then just sticking them in my spare surfing rigs but now I'm not so sure. 

[hal9001]

A 640 is the bare minimum for a dedicated physx card.

[MegaTechPC]

You should really only bother with this if you have a spare Nvidia card lying around to set up for PhysX.  Its definitely not needed and can cause a few headaches to set up and run.  Relatively few games use PhysX to begin with and if you have a decent enough main card it should be able to handle the PhysX on its own...

[GuruMeditationError]

Okay, cool. I'm sufficiently discouraged. :0)

 

I'll stick at 2-way SLI.

 

Thanks so much for the input.

[jmaster299]

Well, in most games it holds true. Still, I don't think there are enough games that really use it to justify another card. I think AC4 uses pretty heavy PhysX too. 

Stop making assumptions about something you clearly know nothing about. All Batman Arkham Games (including the upcoming Arkham Knight), all Borderlands starting with BL2 (meaning the pre-sequel and BL3 as well), both Metro games, Daylight, Star Citizen, Mirror's Edge 1 and 2, the list goes on. Also, regardless of how many games use Physx, anyone running a modern Nvidia card has every right and expectation to take advantage of the feature. 

Also, for the people who say "just switch it to the CPU" that does not work for the majority of Physx titles as most of them only support GPU Physx. Only older Physx titles support CPU Physx.