How PhysX runs on Nvidia and AMD (ATI) systems

Goku · 2011-07-16, 02:14 PM

I have been reading through these forums for hours upon hours, since PlanetSide 2 was formerly and I have been noticing many misconceptions regarding PhysX. Most of the misconceptions is in regards to how PhysX runs on Nvidia and AMD (ATI) systems. The purpose of this thread is to clear up these misconceptions entirely. I know there is threads floating around with information pertaining to PhysX use, but all of that info is scattered and has useless bickering.

PhysX software was originally introduced by Ageia and ran on a PPU (no longer exists) or CPU. Nvidia bought out Ageia in order to make use of PhysX themselves. With the Nvidia buyout you had more developers taking advantage of PhysX and this allowed Nvidia to put the software on their GPUs. A comparable Physics engine is Havoc that is only used on the CPU and in known for being used in the Source engine (HL2, L4D, and TF2).

There is two basic kinds of PhysX. First there is one for Physics that just uses CPU and has no attachment to using the GPU this being the more commonly used one. Second is accelerated GPU PhysX meant for specific types of Physics and this is the less used version being only in under 30 games.

No idea on what kind of PhysX PS2 is going to be using.

How accelerated GPU PhysX runs on hardware is different when running systems with either Nvidia or AMD GPUs. With Nvidia you can run PhysX on the GPU or CPU. On AMD you can only run PhysX on the CPU. There is no way to run PhysX on a AMD GPU.

Unfortunately there is a performance gap between running accelerated GPU PhysX on a GPU vs CPU. Running PhysX on a GPU allows for significantly higher performance then a CPU. If you have an AMD GPU you are going to be suffering a performance loss as result. Though there is a work around for this issue if you have an AMD card. You can get a hacked PhysX driver allowing for a Nvidia card to be used as dedicated card for handling the physics calculations. You can do this normally with a Nvidia card as well to get even higher performance then just making one GPU render and do physics calculations.

Here is a comparison from a review site:

This review used a 980X as the CPU. Even though the 5870 is a stronger card then this weaker version of the GTX 460 by running PhysX on the GPU it gets 2.5 times higher performance with PhysX on high. The 980X is the most powerful desktop processor out now and even that cannot out do PhysX being used on a GPU.

This here shows the GTX 275 being use as a dedicated card for PhysX calculations. You can see the the 5870 with the GTX 275 pairing allowed for a 2.5 times increase in performance with performance being nearly the same as the GTX 460.

What can we gather from all this? Like I mentioned before PhysX at the moment is nearly unable on the CPU. A Nvidia card must be used in someway in order to get proper performance if wanting to use PhysX. Be it using Nvidia as your primary card or having an AMD one plus having a Nvidia card for dedicated PhysX processing.

This is what the current accelerated GPU PhysX looks like. Nvidia is just recently released PhysX 3.0 to developers last month. I do not know if PS2 is being developed with this version. The new version promises greater performance on the CPU, but there is no games using this yet. With no games there is no to know the true performance yet in game with this new version when it comes to GPU vs CPU. There is NO mention of accelerated PhysX being used on AMD cards in this version. If it was it would of been mentioned, so for the time being do not think this version will allow it. Accelerated GPU PhysX still is a way for Nvidia to pull in more GPU sales instead of people going to AMD never forget that. Many developers use it as a way to get funds from Nvidia for helping develop the entire game like the TWIMTBP.

EDIT: Corrected the post as per feedback from Atranox's post.

SwiftRanger · 2011-07-16, 02:45 PM

Originally Posted by Goku

On AMD you can only run PhysX on the CPU. There is no way to run PhysX on a AMD GPU.

Odd, as SOE said otherwise multiple times during the video panels. They also said we could turn off PhysX completely though (compatibility with older rigs) so I don't think it's that important to PS2 as SOE/nVidia want to make us believe. Thx for the info though.

If it's really as "bad" as you say then this is major step backwards for the PC platform. These manufacturer-exclusive features can be neat but only if they're seen as an extra.

Zulthus · 2011-07-16, 02:51 PM

I'm pretty sure it doesn't matter if you have ATI or Nvidia for PS2, since they most likely aren't designing PS2 with Nvidia users in mind. Metro 2033 uses PhysX heavily and I'm able to run it on my CPU with better than average performance on max settings. I haven't played/seen Mafia II, so I wouldn't know how graphics intensive it is.

Zulthus · 2011-07-16, 02:52 PM

Originally Posted by SwiftRanger

They also said we could turn off PhysX completely though

I don't think they did. PhysX in PS2 will make bullet physics possible and give vehicles the ability to fishtail and such. I highly doubt it's togglable.

Rbstr · 2011-07-16, 02:57 PM

It depends on the kind of implementation.

You can have physx for some things, like vehicle mechanics and the like, always active. Then the physx for effects rather than mechanics be togglable.

Goku · 2011-07-16, 03:06 PM

What SOE was saying I believe is that even if you have an AMD card you can still use PhysX by using the CPU. No other way around this issue at the moment.

Last I heard though the Metro 2033 did make use of PhysX to a good extant compared to previous games. I know Metro is considered among many to the Crysis of DX11 in terms of graphics too. If people find it playable all the power to them of course.

Like I mentioned though PhysX 3.0 is going to be taking more advantage of CPU power.

Again this is from the review. It shows the Core i7 980X in terms of scaling with a number of cores. Going to 1 to 2 cores there is a bump in performance, but after that even with 6 cores you have the same performance. If we are lead to believe PhysX 3.0 allows for more multithreading we could potentially at least 2 times the performance of PhysX on quad cores or higher. Going with that it would be smart to even have a quad core for this game if you do not have a Nvidia card.

Even if PS2 doesn't let you turn PhysX off, there maybe a low setting for CPUs to have to better handle the game. Nvidia wanted PhysX for their GPUs to boost sales, so with that I am positive the GPU will still out do the CPU by a good margin.

Hamma · 2011-07-16, 03:08 PM

Very well put together thread thanks Goku

Goku · 2011-07-16, 03:12 PM

You're welcome, Hamma. I will be keeping an eye on this PhysX 3.0 version if there is news on its use and update the OP as needed. I am hoping to see some benchmark from Nvidia showing the CPU improvements soon.

@Swift.

I missed your point on this being bad for PC platform. Many people consider PhysX to be a closed API like CUDA, since at the moment only Nvidia cards can really make use of it. Those people argue there is alternatives like Havok that supports BOTH Intel and AMD cpus even though its owned by Intel that can be used in games. Right now I am hoping this PhysX 3.0 turns the table on this and makes PhysX seems more open source if the CPU can perform at playable levels. Early last year there was a major stink between AMD and Nvidia about this very issue. Lets just say I saw a lot of a lot of threads that turned into everyone being trolls. I do not want this thread to become that as its just to inform those who do not know about it.

artifice · 2011-07-16, 03:15 PM

Nvidia sent Sony a check to gimp ATI cards.

Kietharr · 2011-07-16, 04:38 PM

Originally Posted by artifice

Nvidia sent Sony a check to gimp ATI cards.

Not really, they just wanted a leg up in making sure they hold their spot as the most powerful high performance cards. PhysX 3.0 is improving CPU performance which is basically improving ATI cards while offering nothing to Nvidia users.

Nvidia really can't use physX to gimp ATI cards because a lot of PC gamers use ATI (also both Nintendo and Microsoft use ATI hardware in their consoles), so if their system isn't going to work well on both game developers will simply avoid adopting it which defeats the entire purpose of them buying the technology in the first place.

artifice · 2011-07-16, 04:42 PM

Originally Posted by Kietharr

Not really, they just wanted a leg up in making sure they hold their spot as the most powerful high performance cards. PhysX 3.0 is improving CPU performance which is basically improving ATI cards while offering nothing to Nvidia users.

Nvidia really can't use physX to gimp ATI cards because a lot of PC gamers use ATI (also both Nintendo and Microsoft use ATI hardware in their consoles), so if their system isn't going to work well on both game developers will simply avoid adopting it which defeats the entire purpose of them buying the technology in the first place.

Nvidia has been notorious for intentionally gimping CPU processing for their PhysX engine and intentionally deactivating PhysX when someone uses an ATI card.

There are alternative physics engines that are better than PhysX like Lagoa Multiphysics.

Atranox · 2011-07-16, 05:42 PM

FYI - there is a lot of misinformation in this thread.

Your benchmarks apply to GPU-accelerated PhysX, not the PhysX engine or PhysX processing. GPU-accelerated PhysX is an exceptionally rare feature that has been used by less than 20 PC games. Such games include Mirror's Edge, Mafia II, and Metro 2033. Planetside 2 will almost certainly not be using this type of PhysX.

With GPU-accelerated PhysX, it can only run effectively on the GPU. This can run on NVIDIA cards, but not on AMD or Intel cards. If you do not have an NVIDIA card and you enable this type of PhysX, then it attempts to run on the CPU, which is extraordinarily inefficient as your benchmarks show.

Again, this is not likely to be something that you need to worry about.

Based on SOE's description of what PhysX is being used it - it sounds like PhysX is being used as the physics engine, not for the accelerated GPU effects. The actual engine does not run on the GPU, so it makes absolutely no difference whatsoever whether or not you have an NVIDIA or an AMD card. Many games utilize this engine, such as Company of Heroes, Mass Effect, Dragon Age, etc.

While not confirmed, I'm almost entirely sure that this is the form of PhysX that PS2 would be utilizing. Your GPU brand will likely not provide any form of visual or performance advantage nor disadvantage. Both companies are great and are extremely even right now in terms of pricing, performance, value, drivers, market share, etc.

Unless GPU-accelerate PhysX is being used (very unlikely), then you will not need an NVIDIA card for the best performance or effects.

BorisBlade · 2011-07-16, 06:03 PM

Not being super techy on the coding, is it possible to have a toggle to allow for GPU physX? Would rather not be grouped with those who poorly chose AMD. My system can run the stuff, would like to get the performance advantage of doin so.

Zulthus · 2011-07-16, 06:11 PM

Originally Posted by BorisBlade

Would rather not be grouped with those who poorly chose AMD.

There is no "poor" choice in having either a AMD or Nvidia card. They both work fine and it's a matter of personal opinion.

Goku · 2011-07-16, 06:12 PM

That is a few areas I did not realize. Though when people think PhysX I bet most people think about the GPU accelerated one. I will go through the OP and update as needed shortly. If I take out what is mentioned about PS2 using the accelerated type will the post be correct for the most part?

You do seem knowledgeable on the subject I will say. Do you know anything more in the relation with PhysX 3.0 GPU accelerated PhysX running on CPUs? With what I got from SOE it sounded like it would favor Nvidia cards, but AMD would take a hit.

EDIT: Updated OP as to your concerns Atranox. Please let me know if I should change anything. I want this to be close to accurate as possible.