Making the step from DirectX 9 to DirectX 10 hardware has been difficult for Nvidia and AMD.

Design changes such as adding a geometry shade have yet to produce the promised speed improvements. AMD has made each pipeline fully programmable, so vertex, pixel, physics and geometry operations all go through the same set of transistors.

The Radeon HD 2600XT is the successor to the ATI X1650 chip and becomes AMD’s fastest mainstream product. It includes the impressive features present throughout the Radeon HD 2000 range, one being onboard HDCP keys for protected-content high-definition playback.

The graphics processing unit (GPU) also contains an audio controller so the card can output 5.1 surround-sound audio when using an HDMI connection, with no need for internal S/PDIF connectors – instead the audio works via the PCI Express bus.

Sapphire includes an HDMI dongle with the 2600XT, which connects directly to the card’s DVI output and makes it a one-stop solution for connecting your PC to a high-definition TV. The audio controller driver was difficult to install on our test system.

Another feature unique to all Radeon HD 2400- and 2600-based cards is Unified Video Decoder (UVD) hardware. Combined with Avivo HD software, this can perform H.264, AVC and VC-1 hardware decoding. Rival Nvidia has omitted VC-1 decoding from its cards, which leaves the CPU to process VC-1 encoded HD-DVD and Blu-ray discs.

As well as taking decoding tasks away from the CPU, UVD and Avivo HD increase video quality by avoiding motion blur and sharpening the image.

AMD also includes a hardware tessellation chip, which aims to dramatically improve 3D image quality in compatible games. The chip splits triangles into multiples, resulting in a greater level of perceived detail. According to AMD, three game studios are working on titles to take advantage of a tessellator and it will be part of the DirectX 11 spec due out in 2009.

The GPU is a monster core containing no fewer than 390 million transistors ticking over at 800MHz. Sapphire’s card includes 256MB of GDDR4 memory running at 2.2GHz. Power consumption is low for a modern card and requires no additional power connectors.

It measures 23cm long, dwarfing all other mid-range cards. But it scores points on being a single-slot solution.

On the scores front it achieved 5,994 in 3Dmark06 and 10,398 in 3Dmark05, making it as fast as the 8600GT in these synthetic benchmarks at 1,024x768 running on an Intel Core 2 Extreme X6800, Asus P5W DH Deluxe motherboard, 1GB Ram and Western Digital 10,000rpm Raptor.

Overall it was slower in Doom 3 and Half Life 2 by margins of five to 33 per cent. It really struggled in Fear when anti-aliasing was enabled, becoming unplayable at 1,200x1,024 and beyond. The card was faster than the 8600GT in Unreal Tournament 04 and generally it provides playable frame rates at up to 1,600x1,200 with no anti-aliasing and 1,200x1,024 with 4x anti-aliasing turned on.

It may be a bit slower than the 8600GT, but it draws less power as a result and also has bags more features than Nvidia’s offerings, including free games when you go to Valve’s website. Overall, it’s a good-value graphics card.