Question: Radeon HD 6870 with a dedicated PhysX card

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t3k

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Jul 5, 2013
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Hello,

I've been playing a few games that have the potential to run PhysX (Borderlands 2, Planetside 2) and my jealousy has overcome me, so I'm looking into how difficult it would be to pair my current system with a cheap, dedicated GeForce card for PhysX. I read an article on tomshardware that showed an HD 5870 running PhysX with a variety of nVidia cards as well as using the CPU. With something like a GT 240, the fps was around 30, so playable.

Most of the articles I've been reading about dedicated PhysX cards are based on users with a high end GeForce card, looking to add on a cheaper card just for PhysX. And the answer is always that it's not worth it because it creates a bottleneck and ruins the performance. It was always better to run everything off of the one card.

My setup would be using an HD 6870, which obviously can't do PhysX on it's own. Using the CPU is out of the question for me, because I'd like to be able to max out the graphics options and PhysX is far too intensive to be able to run everything smoothly. My hope was to be able to buy an old, used nVidia card for like $40 and just toss it in with my current setup and add the ability to watch thousands of little bouncing particles in my games, but sadly (as usual with most things pc) it's more complicated than that.

The Question:
So what I'd like to know is whether or not adding a cheap card (like a GT 240) as a dedicated PhysX card would enhance my ability to run games with PhysX or hinder them so much, by limiting performance, that it's no longer worth it.

My Setup:
CPU - Phenom II 965 Black Ed.
GPU - XFX Radeon HD 6870
PSU - 775W (Plenty of power, shouldn't be an issue)
MOBO - M4A88TD-V EVO
RAM - 12gb 1333mhz (Before anyone makes a comment about the amount of memory, I currently work as a video editor, so no, I didn't buy 12gb just for gaming)
I use a widescreen TV as my monitor so I'm only using 1360 by 762 resolution. I know it's bad, but it's cheap and the lower resolution allows my humble setup to max out every game I've come across, except Crysis 3.

Thank you for your time. Anything you have to contribute on this topic would be greatly appreciated.

T3K
 
Solution
17seconds
Several issues:

1) You can get it to work. It's called "Hybrid PhysX" if you do a search. The problem is that the last drivers that supported Hybrid PhysX came out over two years ago, so compatibility with current games is not that good.
http://physxinfo.com/wiki/Hybrid_PhysX

This guide tells how to get it running on Borderlands 2:
http://www.overclock.net/t/1307142/borderlands-2-with-hybrid-physx


2) It seems like you understand that running PhysX through a well-matched PhysX GPU is a good thing and will result in improved performance. CPU PhysX just isn't viable for High PhysX settings. The key is a "well matched" PhysX card. Not enough CUDA processing power, and it will slow down your performance, but a well-matched card...
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skept1k

skept1k

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May 11, 2013
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It completely and entirely possible to do this. I have a friend of mine who's running AMD Radeon HD's in Crossfire with a PhysX dedicated GPU, allowing him to enable PhysX in games. From what I've been told though, it's a real pain in the a** to get it to work smoothly with all the drivers. Don't let that stop you though, if he can get it to work then so can you! As far as performance goes though, you're really not going to experience a real gain in FPS, the PhysX workload is just going to be taken off your CPU (If that's what you set it to) PhysX is, unfortunately, extremely debilitating when enabled. If anything you'll get less fps.
 
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t3k

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Jul 5, 2013
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I should clarify then. At the moment I don't have PhysX turned on at all. The only way to do that would be to add it to the CPU workload and that would make most games unplayable. So right now, I don't have PhysX. My hope was that by adding in a cheap card, I could start to use PhysX. However, when I looked it up all I saw were people saying not to do that because it will ruin your performance. So really, the answer I was looking for was someone to say either: Yes, if you add that extra card to run PhysX, your performance will drop to the limitations of that card, making everything suck. Or No, by adding that card, you will get PhysX, but your 6870 will still perform exactly the same and your FPS will not change.

I guess since both of you are saying that I should not expect an increase in FPS, which I certainly wasn't, that I can at least expect to not see a decrease. But I'd like to hear from someone who understands this problem I keep reading about, saying that it bottlenecks your system. Why is it that everyone seems so adamant about that when the main card is a GeForce, but when I do the same thing in my system that's no longer a problem? If I can understand why these two situations are different, then I can confidently buy myself a PhysX card.

Hope that helps clarify things. Thanks

Sidenote to skept1k:



I'm interested in this setup you're talking about. I've also been thinking about running a second 6870 in crossfire as a separate project. If I do get this PhysX thing sorted, that'd be great to know whether or not I can still run crossfire on top of that. How does he get three video cards working together? Does he just have a huge motherboard or is he connecting the PhysX card some other way? I'm very curious about the details of his setup. Anything you could share would be great.
 
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17seconds

17seconds

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Jul 27, 2010
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Several issues:

1) You can get it to work. It's called "Hybrid PhysX" if you do a search. The problem is that the last drivers that supported Hybrid PhysX came out over two years ago, so compatibility with current games is not that good.
http://physxinfo.com/wiki/Hybrid_PhysX

This guide tells how to get it running on Borderlands 2:
http://www.overclock.net/t/1307142/borderlands-2-with-hybrid-physx


2) It seems like you understand that running PhysX through a well-matched PhysX GPU is a good thing and will result in improved performance. CPU PhysX just isn't viable for High PhysX settings. The key is a "well matched" PhysX card. Not enough CUDA processing power, and it will slow down your performance, but a well-matched card could boost your FPS, roughly, in the ballpark of 25%.

http://www.tomshardware.com/reviews/nvidia-physx-hack-amd-radeon,2764-7.html
mafia2_01.png


3) The GT 240 is probably not the best choice of a card for your needs. At minimum, I would shoot for a GTX 260. The best cards are the recent 600 series cards, since they use less power and generate less heat. The GT 640 is a cheap alternative.

Here is the Tom's Hardware review that shows the impact of various dedicated PhysX cards. It also discusses the issue and how to get it to work, but it's a few years old at this point. You can see that a GT 240 is better than the CPU, but still not the best of these outdated cards. The key is to maximize the number of CUDA cores and core clock speed.
http://www.tomshardware.com/reviews/nvidia-physx-hack-amd-radeon,2764.html

http://www.tomshardware.com/forum/newresponse/1724341
mafia2_02.png
 
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Solution
skept1k

skept1k

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I actually am running Crossfire XFX 6870's on my rig upstairs , absolutely beautiful performance, get's about 150+ constant fps (At least for my rig) on BF3 on Ultra at 1920x1080. As far as my friends rig is concerned I'll ask him about it and I'll message you the details on how he managed to do it. :)
 
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Mousemonkey

Mousemonkey

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Better still, post it here so that we can all see the solution. ;)
 
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skept1k

skept1k

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Sure thing! I only offered to message it to him in case someone had stumbled across the answer before I did. So far, matto17secs's answer is the best you can go on right now.
 
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t3k

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Jul 5, 2013
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Thanks for the responses.

matto17secs, based on what you said, I suppose I can safely assume that doing this will not hurt the performance of my otherwise functional system. It's been very problem free since I've built it and I'd hate to add something that made it dysfunctional. The only thing that's still worrying me is that I see lots of issues running PhysX and I can't tell if my kind of setup would make those problems better or worse. People running one high end nVidia graphics card apparently sometimes get terrible performance from running PhysX just because it's poorly optimized sometimes. It's hard to explain, but I certainly haven't seen a resoundingly positive public opinion on PhysX or it's reliability when used in a game.

skept1k, hey that's great to hear! I've been debating for a very long time whether or not it's actually worth it. I would love to question you more about your experiences so far. The big tradeoff in my mind is between spending more and getting one good reliable card, or less, going crossfire with a second 6870 and having potentially more horsepower, but running the risk that everything might not work with crossfire. And if it doesn't then you're SOL because one 6870 won't really cut it. Have you encountered any issues like this? Or has everything worked the same as having one card? I'd hope that there aren't any added complications. And yes, please let me know what you can about your friend. I'm very interested in what he has to say. That kind of combination could become a very nice upgrade option for me to work on over the next few years.
 
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skept1k

skept1k

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I'll be sure to keep you informed :) As far as my 6870 Xfire setup goes, I have experienced ZERO issues with it. AMD has come a long way driver-wise, they're not as bad as they used to be. Keep in mind though some games are optimized for AMD card and other are optimized for Nvidia cards. An example of each would be BioShock Infinite, and ARMA 3. BioShock Infinite is an AMD optimized game, and on just a single AMD XFX 6870 I was able to get 70+ fps (and higher, with ENB enabled too! Damn that was a stunning game) on ULTRA settings at 1920x1080P resolution. On my current rig downstairs with my EVGA Nvidia 460 GTX SLi setup, I managed to get roughly 38-70+ fps at 1440x900 resolution on ultra, it would get pretty rough, and that's a considerably more powerful setup versus a single 6870, not to mention I have both of my 460's overclocked to 900/1800/3600 which gets me some pretty crazy performance in a lot of titles, love these cards! The fact of the matter is the game wasn't optimized for Nvidia GPU's. Now, ARMA 3 (Alpha version, not totally streamlined and optimized but still gets WAY better results on my 460 SLi rig) as far as I can tell this game is VERY optimized for Nvidia GPU's, I ran the game on Ultra at an average of 55+ fps across all three of my monitors at 4601x900 resolution ( I switch between Surround and single monitors depending on the game, it's not very fun trying to run 3 of them when you only have 768mb of GDDR5 :/, crashes like a bastard a lot of times ) Gameplay was exceptionally fluid. I tried it on my 6870 rig upstairs with crossfire enabled and I was getting 15-22 fps on ultra on only a 1920x1080P monitor. The game is undeniably Nvidia optimized. So, as you can see, Crossfire has its upsides and downsides. I would definitely say that it has more upsides than downsides now though, as you can see a lot more games are becoming AMD optimized, so it can only get better for you from here. I think the extra 6870 is definitely worth it!
 
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