How do I use a second GPU for PhysX?

[PeterSa]

Hello, I'm building a new PC with an i5-6600K and a Gigabyte GTX 1070 G1 Gaming.
I currently have an Asus GTX 960 Strix. Can I use it with the same build for PhysX?
And I don't really understand how it actually works.. Does it perform smoother with more FPS in games? Is it actually necessary or do I just stick with the 1070 alone? lol

thanks

 

[Tbonius]

Installing a second card as a physx card will not increase your maximum fps, but it will give you a slight increase in your minimum fps. When a lot of things start happening, this is when your fps is at its lowest. If you have a dedicated physx card, your primary card just has to do the graphics processing.

 

[bystander]

Adding a PhysX card will only help in games which have GPU accelerated PhysX. The vast majority of games do not use GPU accelerated PhysX. Only do it if you are playing one of these games and actually could use a boost in performance. When it is used, the 2nd GPU will handle the PhysX calculation, allowing your primary GPU to focus on other tasks.

 

[photonboy]

Tbonius has some misinformation.

1) PhysX is NVidia's physics calculation software.

2) With a single GPU for everything it uses some of its calculation time to do the physics (PhysX) calculations.

3) To use a dedicated GPU for PhysX you can change this in the NVidia Control Panel.

4) FPS?
If the GPU card is fast enough the FPS will increase (unless it's already capped with VSYNC i.e. 60FPS for 60Hz monitor, or if the CPU is the bottleneck). This is because the main card doesn't have to do PhysX calculations so can spend more processing on everything else it does.

However, if the card is too slow the main GPU has to WAIT for it to finish thus the dedicated GPU is the bottleneck and can actually drop performance.

5) As said above, only a few games use PhysX (so other games aren't affected).

6) BATMAN games can be significantly affected by this, however with a GTX1070 already there may be no point.

7) Go ahead and experiement:
a) GAME without PhysX card (repeatable area or benchmark like in Batman Arkham series)
b) GAME with PhysX card in the same area

Summary:
- can help, but must test per game
- enable in NVidia Control Panel
- FPS increase may not warrant the extra card noise (especially if FPS goal is already achieved)

Update:
The FPS increase depends on how much physics is going on. It may help MORE than you might think as the physics is often a sudden thing like a SMOKE GRENADE so the average isn't the best score to go by. Unfortunately the "LOW FPS" score can be affected by other things so benchmarks may not indicate how much it helps. Real gameplay can indicate how often a PhysX effect causes stuttering.

If the PhysX was normally about 30% of the calculation time then if the dedicated card was fast enough you can free up the main card so that 30% is used to increase FPS.

So expect roughly between 0% and 30% gain from what I've seen based on the hardware. Again, PhysX is often some eye candy that suddenly drops FPS causing stutter. This may help with that.

 

[photonboy]

http://www.volnapc.com/all-posts/how-much-difference-does-a-dedicated-physx-card-make

A bit complicated to read. Ignore SLI results.

The dedicated GPU used here is WEAKER than yours, but so is the Titan compared to GTX1070 so it's probably a good comparison to your rig.

In the first game, the Titan alone got 73FPS, but adding the PhysX card jumped to 105FPS average. Wow!

 

[iamacow]

From my experience using older cards for physx is worse than the CPU. The new card is just waiting for the information from the older geforce (physx) card, resulting in low fps. I got even weirder results with SLI and a dedicated Physx card. In this case Titan SLI with a GTX 770, which gave me 5fps less than just leaving it on auto with no 770 installed.

Its not going away anytime soon. Nvidia Gameworks which is basically Physx with extra things is only getting stronger with more features. Though games like Witcher 3 uses the CPU for Gameworks instead of the GPU. Maybe higher compatibility since it was on the consoles too which are AMD based.

So if you want a dedicated physx card, either you need something powerful enough not to slow down your main card or just go SLI.

As this point, I would not suggest using a second card for Phyx unless its the same series. You will lose performance using a 1070 and a 960.

The only time I've ever gotten a performance boost was with using the exact same card and at that point why not just SLI and get even higher performance.

If you have the cards go for it, but if you bench games, you'll find a lower fps as everything waiting for the slower card.