This is a review of the Asus PhysX P1 PCI card with 128MB of RAM, but that immediately raises the question; "What the heck is a PhysX card?"

When you play a game, the CPU and graphics chip have a number of tasks to perform. The CPU loads the game, controls the artificial intelligence of the characters and keeps tabs on the location of all the objects and players as they move around to make sure that you don't walk through solid walls or float in mid-air. The specialised graphics chip makes everything look realistic and impressive on your screen by adding textures, colours and lighting effects.

At present the physics of a game are handled by the CPU, so when you shoot an enemy you'll see blood spray, his helmet go flying and then the corpse slumps to the ground. The CPU already has plenty of jobs to perform so the physics are relatively limited, which is why an explosion doesn't cause a barrel to disintegrate into hundreds of fragments, but instead it flies into three or four parts in a relatively unrealistic fashion.

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Ageia, a new start-up company, has developed its PhysX engine to allow games developers to offload the physics workload from the CPU to a dedicated chip which is mounted on a PCI card. The card looks much like a regular graphics card with memory chips and a heatsink and fan, except that it doesn't have any output connectors. The workload of the game is handled by the CPU and PhysX card which then send the results of their labour to the graphics card, which in turn produces the frames that you see on your screen.

You won't get any benefit from PhysX unless your game supports the feature, which presently means Unreal Tournament 2007, Rise of Nations: Rise of Legends and Tom Clancy's Ghost Recon Advanced Warfighter (or GRAW for short). Asus and BFG have licences to produce 128MB PhysX cards while Asus has the exclusive on the 256MB version which is likely to go on sale in a couple of months' time.

The idea is that a physics card will remove a performance bottleneck in a top-notch gaming PC, so we installed two Sapphire X1900 XT graphics cards in CrossFire on a Sapphire A9RD580 Adv motherboard with an Athlon 64 FX-60 processor and played the copy of GRAW that Asus bundles with its PhysX card.

As you would expect, the game played smoothly on such an epic system, at a resolution of 1,600 x 1,200 and all the high quality settings enabled. We then tried to install the Asus PhysX card but the drivers wouldn't install correctly, so we reverted to a single graphics card, installed the PhysX card and then re-installed the second graphics card. This worked perfectly well, but blimey, what a pain.

When we played GRAW with PhysX the game looked noticeably better, as there were many more particles and fragments flying around, but the graphics cards were clearly struggling to handle all of these extra bits and pieces which required textures and lighting to make them appear realistic.

GRAW is the first game to support PhysX so it clearly cannot make the hardware a requirement, otherwise the 99.9 percent of the market which doesn't own a PhysX card wouldn't be able to play it. Instead PhysX adds some extra eye candy that enhances the gameplay, but it makes your PC work incredibly hard to get the most from the new hardware.

The Asus PhysX card is an interesting piece of hardware that makes supported games look very impressive, however there are a number of caveats. This is new technology and so far the list of games is very short. It costs over £200 and you need a top-line gaming PC to make it work properly. We have little doubt that Unreal Tournament 2007 will look spectacular with PhysX, but until then the jury's out.