The Radeon brand has a long and proud history, but for the past year ATi – the graphical wing of AMD – has been playing catch-up. Its mid-range Radeon HD 2000 cards may have found a niche in the value market, but it’s rival Nvidia that has set the pace, consistently bringing more powerful graphics hardware more quickly to market.

But AMD is no quitter. Rather than be left behind, the company has boldly retired its entire range of DirectX 10 graphics cards just nine months after launch, replacing it with the updated HD 3000 series. The new cards use a 55nm fabrication process, promising lower costs and power consumption than the 65nm and 90nm wafers AMD used before (and which Nvidia still uses).

The new cards also support DirectX 10.1, which permits more powerful lighting techniques than the original release of DirectX 10 – although it remains to be seen whether developers will target the new routines that aren’t currently supported by Nvidia.

We weren’t blown away by the first two cards in the new range, the HD 3850 and HD 3870. They’re relatively affordable, costing around $260 and $290 respectively, but in our tests they seemed a little underpowered for modern games.

AMD’s new X2 card, however, has the potential to really shake things up.
As the name implies, the HD 3870 X2 is built around two HD 3870 ASICs mounted on a single card. This isn’t a huge technological breakthrough – it’s fundamentally the same as running two 3870s in a CrossFire configuration.

Indeed, while Windows sees it as a single device, CrossFire sees it as two cards. That means motherboards using the new CrossFireX system, which can theoretically support four cards at once, will drive a maximum of two X2s.
Not surprisingly, the X2 thus offers the same feature set as the 3870, including hardware HD video decoding and software power management. Software overclocking will also be possible once an X2-aware version of AMD’s Overdrive applet emerges.

The cramming of two GPUs into one card results in a bulky physical design, and a board that’s so long that, if you don’t have a full-sized tower case, you might need to shift some drives around to accommodate it. It demands two power connectors, too – a pair of six-pin plugs will drive it, but you can optionally swap one for an eight-pin plug to give a little extra juice for overclocking.

Despite the twin cores, it’s not alarmingly power-hungry: under load it added just 120W to our test rig’s total consumption, comparable to an Nvidia 8800 GTX.
But while the card itself may be ungainly, you can’t argue with the maths.

Doubling the 3870’s 320 stream processors gives the X2 a ridiculous 640 shaders to play with (the 8800 GTX and Ultra have 128), with 32 texture units and 32 raster operators. There’s a gigabyte of dedicated RAM too, with support for both GDDR3 and GDDR4. As a result, where a single 3870 can’t quite get the best out of modern games, the X2 romps through them.

When we ran our Crysis benchmark on an Intel Quad Extreme-based test rig at 1600 x 1200 with high detail, a single 3870 managed an average frame rate of 24fps. In the same test, Nvidia’s 8800 GTX scored 29fps. The 3870 X2 achieved an impressive 31fps – equal to a stock 8800 Ultra.

In the shader-intensive Call of Juarez benchmark the X2 did even better. At 1600 x 1200, again with detail set to high, it averaged a remarkable 38fps. In the same rig, Nvidia’s 8800 Ultra, with its comparatively meagre shader count, managed just 22fps.

These are head-turning results, but sheer graphical power is only one part of the formula. Sure, some enthusiasts will pay whatever it takes to get the best performance, but if AMD is to convincingly reassert itself in the mainstream it needs to be competitive on price as well.

The good news is that, next to both AMD’s other offerings and the competition from Nvidia, the X2 is great value, with Sapphire’s launch board coming in at $542. By comparison, a 768MB 8800 GTX can be had for around $768, while an 8800 Ultra will set you back $1000.

It only occupies one PCI-E slot, and it will run on any motherboard without the need for CrossFire support. As a further sweetener, AMD has clocked the stock X2 core at 825MHz, a 50MHz speed boost over the standalone 3870.

All told, the HD 3870 X2 is AMD’s most exciting graphics product in years. Arguably, it’s only a simple, incremental improvement, but it’s a big increment, big enough to present a convincing challenge to Nvidia’s hold on the high end. And there’s plenty of scope for prices to fall and clock speeds to rise.

Nvidia won’t take this lying down, of course. The venerable G80 GPU, which powers 8800 GTX and Ultra cards, is already well over a year old, and its new 9000-series cards are on their way to our Labs as we write this. But today belongs to AMD, which has at last delivered a winner.