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Analysis: PhysX On Systems With AMD Graphics Cards

GPU PhysX: What Card Is Best?

How much do you need?

Generally, faster is better. Of course, it would be nonsense to use a GeForce GTX 480 as a dedicated PhysX card. Even using a rather expensive GeForce GTX 285 could hardly be called economically sensible. But let's take a look at our Mafia II benchmarks.

Again, we chose this game because of its very good compromise between physics and traditional graphical effects. Cryostasis uses a disproportionate amount of PhysX. Conversely, Metro 2033 is too heavy on graphics to make a good gauge of PhysX-based performance.

Looking at the graph, you can see very clearly that a card slower than a GeForce GT 240 or 9600 GT makes little sense, even if it should be able to support PhysX in theory. Using a GeForce 8400 GS is actually 15% slower than using a single GeForce GTX 480, which is extremely counterproductive. We therefore left those results out of the chart.

What PCIe slot is good enough?

A popular question centers on how fast the PCIe slot for the PhysX card needs to be. We used a motherboard with PCIe slots of different speeds, measuring speed simply by moving the PhysX card around between them.

Clearly, a faster card is slightly bottlenecked by a x4 slot compared to the other two. The difference between x8 and x16 is so marginal that it can be disregarded. A GeForce GT 220 is too slow to notice any difference, as would be a GeForce GT 240 and a 9600 GT. Even the GeForce GTX 285 doesn't suffer that badly. A x4 slot seems to be OK, though a x8 slot is the safer bet for faster cards.

Assessment

In the end, it comes down to cost. Spending $80 on a used GeForce GTS 250 will bring your computer with a Radeon HD 5870 to the same level of PhysX performance as a single GeForce GTX 480 card. However, the combined cost of these two cards is higher than the single GTX 480. Real added value is obtained only by using an additional GeForce GTX 260 or better. This is where costs get out of hand and scare everyone but true enthusiasts away. We would only recommend adding an additional card if you already have a spare lying around due to a recent upgrade, for example. Then the effort might be worthwhile, even if the extra idle power consumption might gnaw at your consciousness.

  • eyefinity
    So it's basically what everybody in the know already knew - nVidia is holding back progress in order to line their own pockets.
    Reply
  • Emperus
    Is it 'Physx by Nvidia' or 'Physx for Nvidia'..!! Its a pity to read those lines wherein it says that Nvidia is holding back performance when a non-Nvidia primary card is detected..
    Reply
  • It looks like the increase in CPU utilization with CPU physX is only 154%, which could be 1 thread plus synchronization overhead with the main rendering threads.
    Reply
  • eyefinity
    The article could barely spell it out more clearly.

    Everyone could be enjoying cpu based Physics, making use of their otherwise idle cores.


    The problem is, nVidia doesn't want that. They have a proprietary solution which slows down their own cards, and AMD cards even more, making theirs seem better. On top of that, they throw money at games devs so they don't include better cpu physics.

    Everybody loses except nVidia. This is not unusual behaviour for them, they are doing it with Tesellation now too - slowing down their own cards because it slows down AMD cards even more, when there is a better solution that doesn't hurt anybody.

    They are a pure scumbag company.
    Reply
  • rohitbaran
    In short, a good config to enjoy Physx requires selling an arm or a leg and the game developers and nVidia keep screwing the users to save their money and propagate their business interests respectively.
    Reply
  • iam2thecrowe
    The world needs need opencl physics NOW! Also, while this is an informative article, it would be good to see what single nvidia cards make games using physx playable. Will a single gts450 cut it? probably not. That way budget gamers can make a more informed choice as its no point chosing nvidia for physx and finding it doesnt run well anyway on mid range cards so they could have just bought an ATI card and been better off.
    Reply
  • guanyu210379
    I have never cared about Physics.
    Reply
  • archange
    Believe it or not, this morning I was determined to look into this same problem, since I just upgraded from an 8800 GTS 512 to an HD 6850. :O

    Thank you, Tom's, thank you Igor Wallossek for makinng it easy!
    You just made my day: a big thumbs up!
    Reply
  • jamesedgeuk2000
    What about people with dedicated PPU's? I have 8800 GTX SLi and an Ageia Physx card where do I come into it?
    Reply
  • skokie2
    What is failed to be mentioned (and if what I see is real its much more predatory) that simply having an onboard AMD graphics, even if its disabled in the BIOS, stops PhysX working. This is simply outragous. My main hope is that AMD finally gets better at linux drivers so my next card does not need to be nVidia. I will vote with my feet... so long as there is another name on the slip :( Sad state of graphics generally and been getting worse since AMD bought ATI.. it was then that this game started... nVidia just takes it up a notch.
    Reply