Wherever Nvidia treads, ATI must surely follow. Or is it the other way round?

With their latest 3D chipset launches, Nvidia and AMD's PC graphics subsidiary have once again mirrored each other extremely closely.

Nvidia in disguise?

There's an absolutely uncanny resemblance between ATI's new Radeon HD 3800 series and Nvidia's GeForce 8800 GT.

More than anything, both chipsets aim to bring the performance and features of current high end DirectX 10 3D cards down to a much more mainstream price point. The only differences are in the fine details and final pricing.

For the 3800 series, ATI has essentially subjected its existing flagship DirectX 10 GPU, the rather underwhelming Radeon HD 2900 XT (also known as R600), to a die shrink from 80nm to a finer 55nm node. That alone makes for a much smaller, cheaper and more power efficient GPU. ATI reckons both performance per watt and bang for buck are both doubled with the 3800 series.

It also makes for cards that work with a wider range of systems. The entry level Radeon HD 3850 model is a single-slot board, while the top-end Radeon HD 3870 is a full dual-slotter. However, like its slimmer sibling, the 3870 requires only one six-pin supplementary power connector. The implication is obvious: You don't need a pricey 1,000 Watt power supply to runs these cards, even in multi-GPU configurations.

More to the point, you won't need to spend much on the boards themselves, at least compared with the outgoing 2900 XT. The 3850 is yours for just £110 including VAT. The 3870 will sell for as little as £140.

As for speeds and feeds, core clock frequencies for the 3850 and 3870 are 670MHz and 775MHz, respectively. Meanwhile, the 3870 packs 512MB of exotic GDDR4 memory running at 2.25GHz. The 3850 makes do with 256MB of more pedestrian 1.66GHz GDDR3 memory.

Architecturally, however, the two models are identical and mostly match the outgoing Radeon 2900 XT. All 320 stream processors are present along with 16 texture units and 16 render output units.

Less memory

The only victim of ATI's quest for a smaller, more affordable chip is the memory controller, downgraded from 512-bit to 256-bit. For the beefier 3870 chipset, ATI claims that has been offset by the faster memory and optimisations to the memory controller.

ATI has also used the six months or so since the launch of the 2900 XT to add a few new features. First up is support for the upcoming 10.1 revision of Microsoft's DirectX platform. There is much debate over the value of DirectX 10.1 compared with 10.1.