Home More... Featured Articles PhysX PPU From AGEIA... A Real Future?
PhysX PPU From AGEIA... A Real Future? PDF Print E-mail
Written by Starfox   
Tuesday, 30 May 2006 18:00

PPU, in case you're asking, stands for Physics Processing Unit. It's a processor like the GPU on your graphic card but dedicated to physics calculations in applications (mainly games). Physics is a good thing to add some reality to a game like when you shoot a barrel and that it flies in the air instead of sticking to the ground. Since the first PPU cards will be released shortly it's a good thing to think about what they can do and what they cannot do. Read the full article for more.

Right now there is two ways of calculating physics in games and a third one that is not available yet but that people are working on, plus a fourth one that is not really new and just derived from the first.

The first way is the common one, the one that is used by any game released until now that uses a physics engine. Letting the computer CPU taking care of that. The best exemple is the Havok engine used in Half-Life 2 and Oblivion. Those who played these two games already know the limitations of this technique. The CPU already has a lot to do in games so stressing it with physics calculations often result either in a certain inaccuracy of the physics or a slowdown of the whole game. The main problem though remains that one cannot introduced more than a certain number of physics calculations in a game in order to not draw to many CPU resources from other tasks.

PhysX Principles From AGEIA PhysX Principles From AGEIA

The second way is to use a dedicated processing unit to relieve the processor from physics calculations so it can focus on other things. That's the way used by the company AGEIA which is the first one to deliver a PPU called PhysX for implementation on dedicated PCI cards. Of course this way could be considered the best one like graphic cards are the best way to deal with graphics in a game since a PPU allows for much more physics effects to be displayed at the same time. In the facts it has some drawbacks though. The first drawback is obviously to buy a PPU card, so another piece of hardware for your computer. PPU cards won't be cheap either since the two first models will be sold at $250 and $300 (which is the price of a good mainstream graphic card). The second drawback is that like the first 3dfx card in its time, PPU cards will need PPU enabled games to work and they are not that much around (though existing games could be patched to work with a PhysX PPU).

PPU Card From ASUS

The third way to deal with physics is not available yet other than in prototypes but people are working on it and when I say people I talk about heavy names like NVidia, ATI and Microsoft. NVidia and ATI are researching a way to deal with physics calculations via the GPU of their graphic cards and Microsoft is somewhat helping them by developing an extension to DirectX called DirectPhysics; this extension will be a part of the future DirectX 10 (that Microsoft will probably call something like DirectX SupaDoowaZoowa because 10 is not a selling point -- but I'm digressing). The fact is that both NVidia and ATI would like to use their SLI solutions to let the second GPU take care of the Physics calculations. Even better, HIS recently presented a double ATI VPU card (based on the X1600 XT) where the second GPU could perfectly be used for physics without the need to buy a complete SLI rig. In my opinion that could be the best solution for everyone... AGEIA aside maybe.

And finally there is a last way derived from the first one so it is not really new: to let the CPU deal with the calculations... again. But this time AMD and Intel are pleading for their famous Dual Core CPUs. A dual Core CPU is a CPU containing two CPU cores on the same chip, so to simplify it's two CPUs in one. Dual Core CPUs are still expensive today but will be widely available in the future and there's just about no game using the two cores to their max. So the idea of Intel and AMD is "why not let the game use the second core for physics calculations?".

So finally, AGEIA is unloading its PPU solution with some heavy competition around and an uncertain future. Most people will be repelled by the idea of buying yet another expensive piece of hardware to deal with their games not to mention that the first examples of PhysX in real games (and not in AGEIA demos) are not that impressive (at least it doesn't justify for me to put $250+ in a card) especially when you see the first performances tests in the few PhysX enabled games around which show either no gain in framerate (Ghost Recon Advanced Warfighter case with the same framerate PhysX enabled or disabled) or even worse, a framerate almost cut in half (Bet On Soldier 1.3). Why PhysX would slow down a game? Explication could be nuemrous and are not in the scope of this article. Note however that Ghost Recon Advanced Warfighter is a special case since it uses PhysX for a small number of effects (mostly particle ones) and keep using Havok for the rest -- that might explain why the framerate remains the same.

Ghost Recon Advanced Warfighter PhysX Disabled Ghost Recon Advanced Warfighter PhysX Enabled

Performances put aside there is technically a thing that bothers me: both PPU cards that will be proposed (one from ASUS and one from BFG) have a graphic card like fan on them which tends to suggest that the PPU produces a good amount of heat. In a time where every user tries to cool their case that seems stupid to me to add another heat producer in a computer. There are already the CPU, GPU, motherboard chipset, high speed hard-drives and even the last generation of high power sound cards (Creative X-Fi) producing heat in the system and we already have too many fans in there to cool things down not to mention that multiplying hardware parts is also adding to the electrical consumption and to the power needed by the system to run stable. Put a PhysX card in a SLI system and you obtain a nice heater with the noise generation capability of a boeing about to take off. So why adding another piece of hardware if we can do physics calculations with existing hardware, be it a dual-core CPU or dual GPU graphic cards or SLI solutions?

The ATI GeMini dual GPU solution from HIS - What the physics calculations could be.

Then finally, the PhysX card might as well be dead before even its launch if we take a look at the next generation of motherboards. Next high-end motherboards will embark 2 PCI slots at best. If you want to put a good sound card (instead of the basic motherboard one) and a PPU card, you get a full house (because apparently manufacturers are reluctant to create PCI-E cards other than graphic ones, go figure). Not to mention that with some graphic card, the first PCI slot is blocked so you'll have to choose between the sound card or the PPU card. There is also the fact that profesionals will tell you that it is unwise -- although possible -- to put a card in the PCI slot the closest to the graphic card because of troubles with heat dissipation. All of these factors don't introduce a good omen for the future of another piece of gaming hardware.

Eventually, the future will tell us what option is judged the best by users. Myself I would favor either the use of the second core on a Dual-core CPU (the easiest and safest but probably not the best way on the long run) or even better the inclusion of a dedicated processing unit in graphic cards which seems to me far more logical than a dedicated card. Do I believe that PPU has a future? The answer is yes, to some extent. Do I believe that it has a future in its current form with the PhysX PPU of AGEIA? The answer is no. NVidia already proved that it is possible to make two 7900 GTX graphic cards run on the same PCI-E slot and ATI even proved (like 3dfx in its time) that it's possible to run to GPUs on the same card so it is ok to imagine that the second GPU could be either replaced by some form of PPU or could deal with physics calculations letting the user decide to use it as a pure SLI graphics solution or for enhancing the physics. A dedicated card is not and shouldn't be required.

But well, I've been wrong before and experience of the past shows that users tend to favor weird and barely practical solutions because they look cool (it's the reason why we got the VHS over the Betamax or Video2000 and the reason why the Blu-Ray format actually stands a chance against HD-DVD despite of similar capabilities).


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