ATi Radeon HD 2000

Nvidia's six-month reign as sole supplier of DirectX 10 graphics hardware comes to an end this month, as ATi (now owned by AMD) launches its long-awaited Radeon HD 2000 series. The range includes chips for both desktops and notebooks, all of which feature dedicated hardware for decoding HD content, plus a range of measures to reduce power consumption.

Architecture

The first card to appear will be the high-end HD 2900 XT, which should be in the shops imminently. Like Nvidia's current GeForce 8000 range, it's fully DirectX 10 compliant and based on a unified shader architecture. It features 320 stream processors and a 512-bit memory bus - impressive figures next to Nvidia's top-end 8800 GTX, which has only 128 stream processors and a 384-bit bus.

The benefit is offset by slower clock speeds, however: stream processors and RAM run at 742MHz and 828MHz respectively, while the 8800 GTX uses 1.35GHz and 1.8GHz. Running our 3D benchmarks under Vista, the HD 2900 XT's average frame rate proved around 20% faster than an 8800 GTX in Company of Heroes, but only on a par with a lowlier 8800 GTS in Oblivion and Call of Duty 2. Performance was even slower under XP. AMD promises more impressive results in DirectX 10 games, claiming its geometry shading (which isn't used by current DirectX 9 titles) is "50 times faster" than Nvidia's. Although it won't confirm rumours of a souped-up "2900 XTX" card, there's scope to increase clock speeds too.

In addition to the standard DirectX 10 functions, AMD has added hardware tessellation capabilities to its new card, enabling designers to selectively subdivide vector surfaces on-the-fly. This new engine can hugely improve rendering performance, but it remains to be seen whether developers will wish to tie themselves to ATi hardware by using it. Speaking at the launch event, AMD engineer Natalya Tatarchuk acknowledged this was a concern: "We will make algorithms available to work on our competitors' hardware in a similar fashion, but will the performance be the same? I'd be surprised."

The range

The HD 2900 XT will be followed in July by the HD 2600 and HD 2400, each of which will be available in standard "Pro" and higher-specification "XT" variants. 2600 series cards will have 120 stream processors and a 128-bit bus, while the 2400 will have just 40 processors and a 64-bit bus. Processing power is said to range from 42 GigaFLOPS at the low end to 192 GigaFLOPS for the HD 2600 XT and 475 GigaFLOPS for the high-end HD 2900 XT.

Laptops using the new Mobility Radeon chipsets are also expected to appear in July from Acer, Asus, Samsung and Toshiba. DirectX 10-compliant chipsets will come in 2400 and 2600 variants, and there will also be a low-end DirectX 9.0c-only 2300 chipset, aimed at non-gamers wishing to take advantage of ATi's new HD decoder.

Power consumption

The HD 2000 series also includes a range of features aimed at reducing power consumption. The new GPUs can automatically reduce their clock speed during periods of low load, and even switch off logic areas entirely when they're not needed. Most of the cards and chipsets make use of a new 65nm process, requiring less cooling and further reducing power drain. Entry-level cards don't even have a fan.

Prospects

High-end gamers will be disappointed that AMD hasn't focused on raising the stakes in terms of performance, but the company believes its new range will compete on value. UK prices are yet to be confirmed, but Vijay Sharma, AMD's director of Desktop Discrete Products, insists European prices "shouldn't" exceed the US price plus VAT: if this holds true for Britain, prices will start at just £60 for the HD 2400 Pro, rising to around £240 for the HD 2900 XT. As Nvidia releases its mid-range 8600 series, we can expect to see it rethink its high-end 8800 GTS pricing too. The good news is that the battle for the DirectX 10 market has just begun.

Author: Darien Graham-Smith