If you've been waiting a long time for the new HD2000 series from ATI then wait no more. ATI's first DirectX 10 graphics chip, the HD 2900 XT is here. The Asus HD 2900 XT comes in a comprehensive package with the card, the Black Box promotion (including Half Life 2, Team fortress 2, Portal and Half Life 2: Episode 2) and a copy of S.T.A.L.K.E.R all included, giving you maximum value for your purchase.

Compared to ATI's previous high-end chip, there's been no increase in the quantity of memory, or at this stage, to the type of memory. However, the 512MB of GDDR3 RAM that's built into the Asus HD 2900 XT now has a 512-bit memory bus to shuffle data around. The core clock has been given a hike up to 740MHz, while the memory clock sits at an effective 1650MHz.

Although it doesn't quite hold up to the performance of the NVIDIA 8800 GTX cards, or even remotely close to the 8800 Ultra (see Asus GeForce 8800 Ultra), it still handles games very well and has some nice features that may potentially add to the visual quality of a game should developers decide to utilise them. It also comes at a more reasonable price.

As a necessary step forward, and a means of putting the new DirectX 10 application programming interface (API) to good use, the new HD 2000-series has had a complete architecture overhaul. The new unified shader architecture allows a more efficient, more dynamic allocation of the card's resources and adds some new features to accommodate DirectX 10.

Unlike the Radeon X1900-series, which used pixel shaders and vertex shaders to render scenes, the new unified architecture uses stream processors, which can handle pixel and vertex data, as well as the new geometry shading introduced by DirectX 10, and it may also get used for physics processing down the road.

The stream processors used in the Radeon are similar in nature to NVIDIA's own stream processors, but the number of them is far greater. For example, the Asus HD 2900 XT uses 320 stream processors, while 8800 GTX-based cards use just 128. However, the cards differ enough that not direct comparison based on sheer number of stream processors can be made. The most interesting task that is handled by these stream processors is geometry shading. Technically, geometry shaders aren't really shading. They are processing geometrical data, but now they do more of it simultaneously than was ever possible before, therefore doing their job faster and more efficiently.

Without going into too much detail, geometry shaders help reduce the amount of data that needs to be processed. This applies to operations that have been around for a long time, as well as opening the gates for processes that might have been overly taxing on the GPU before. One neat feature of the geometry shader is its limited ability to tessellate polygons -- taking single triangles and sub-dividing them into smaller triangles. This can be used to smooth or add detail to objects, or simply to reduce the amount of initial triangles, while still producing a high-detailed image on the screen.

The HD 2900 XT also has its own dedicated tessellation unit, similar to the Xenos GPU used in the Xbox 360. It can be used in pretty much the same way as the geometry shaders, though it's got a lot more tessellating grunt under its belt. Unfortunately, at present the tessellation unit is not part of the DirectX 10 specification, so game developers will have to write it into their games separately, which may be a deterrent. However, the similarity to the Xbox 360 chip will hopefully draw developers to the idea as there's plenty of potential there.

In our benchmarks, it scored right where it's aimed -- just above NVIDIA's 8800 GTS. In 3DMark06, using the default settings (1280x960, no antialiasing [AA] and no anisotropic filtering [AF]), it scored 11070, where the Asus EN8800GTS 640 scored just 9309. In FEAR, using a resolution of 1280x960 with 4xAA and 16xAF, the card averaged 87fps (frames per second), a touch above it's 8800 GTS competitor, which managed 83fps.

While the card uses one PCI Express x16 slot, the cooler makes sure the adjacent slot, whatever that may be on your motherboard, is made inaccessible. Power is supplied via two PCI Express 6-pin power connectors, though the card actually ships with one 8-pin connector and one 6-pin connector.