The Radeon HD 5870 certainly grabbed our attention when it appeared several months ago. Not only was it ready for Windows 7's next-gen DirectX 11 graphics, but it matched, and occasionally beat the top-dog nVidia GeForce GTX 295, making it arguably the fastest card available.
See also: ATI Radeon HD 5870 review
The 5870, though, was destined only to test the ground for the real trailblazer - the dual-GPU Radeon HD 5970. As in previous years, ATI launched its main chip first, then doubled it up a few months later. You don't necessarily get twice the performance, but the speed boost is hard to resist - inded, nVidia's flagship GTX 295 is itself a dual-GPU version.
So, the 5970 gives you two chips for, well, almost twice the price. This version - the Sapphire Radeon HD 5970 - is cheaper than, for example, that made by HIS; but its £530 price tag is still eye-watering, around £200 more than a standard 5870.
The Sapphire Radeon HD 5970 is a very substantial card. At 309mm long, it's almost 25mm longer than the already huge 5870. Although clock speeds have been dropped in order to keep a lid on power consumption, it's still demanding a lot of mains power. ATI's spec puts it at a 294 watt peak, and even sat idling it draws 51 watt. These figures are considerably above the 5870, cited at 188 and 27 watts respectively.
Not all that incoming power directly pushes pixels of course. Much is turned into unwanted heat, requiring some serious - and noisy - fan cooling to avoid meltdown. Our system topped 50dB on the sound meter - the Sapphire Radeon HD 5970 is one loud card, if not actually the noisiest we've ever witnessed.
You'll need one 8-pin and a 6-pin connector to power the Sapphire Radeon HD 5970. Another oddity is the absence of HDMI. Instead, you get Mini DisplayPort, a licence-free HDMI rival that looks set to muddy connector waters further. While a cheap adapter will convert it to HDMI, it's slightly irritating that just as cards are standardising on HDMI, another alternative is vying for attention.
Overall specifications tend to get toned down when a graphics card is built around two GPUs. In the case of the Sapphire Radeon HD 5970, its specs look nearly identical to those of the cheaper 5850, although Sapphire has managed to tune its 5970 with a smidgen of overclocking, compared to the ATI reference.
See also: Sapphire Radeon HD 5850 1GB review
The core clock of 725MHz has been nudged to 735MHz, while the memory clock goes up to 1010MHz (4040MHz effective). These are tiny increments, it's true, but they do bring the numbers a fraction closer to the single-chip 5870.
On paper, the 5870 remains more impressive (with core and memory clocks of 850MHz and 1200MHz). But the dual-chip architecture rockets the Sapphire Radeon HD 5970 to an emphatic memory bandwidth of 256GB/s (way ahead of the 5870's 153.6GB/s); and overclocking pushes this to a final figure of 258.6GB/s. The 5970 comes with a heavyweight 2GB RAM - 1GB for each GPU - while its all-up tally of 3200 stream processors is, frankly, amazing.
The battle for top speed between ATI 5870 and nVidia 295 may have been inconclusive, but there can be no doubt this time - the ATI 5970 is the card to buy for ultimate performance.
See also: nVidia GTX 295 review
See also: ATI Radeon HD 5870 review
In Far Cry 2 at 1680x1050, the Sapphire Radeon HD 5970 cruised at 114 frames per second, destroying the 5870 and GTX 295 on 89 and 87fps respectively.
See also: Far Cry 2 review
At 1920x1200 a similar lead was witnessed - 109fps playing against the 80 and 79fps of the 5870 and 295. In Crysis, it was also comfortably ahead, notching up 66fps at a resolution of 1600x1200, rather than 45 and 46fps.
In World in Conflict, the Sapphire Radeon HD 5970 scored 71fps at 1680x1050, generally finishing 14-15fps ahead of its competitors; although in Left 4 Dead, its score of 121fps put it only a couple of frames ahead of the 5870 - this game is relatively easy on the PC.
See also: Left 4 Dead review
While comfortably ahead, it's worth noting that in our tests there was rarely much difference in resolutions, moving from 1680x1050 to 1920x1200, suggesting that today's games are not demanding enough to really stretch this card. At even higher resolutions though (think: multi-monitors), expect the Sapphire Radeon HD 5970 to wipe out the likes of the 5870 and the GTX 295.
We also tried the Sapphire Radeon HD 5970 with the new Stalker Call of Pripyat, to benchmark DirectX 11 performance. We didn't have a 5870 to compare, although the 5970's score of 114fps at 1680x1050 left the cut-down Radeon 5850 gasping for air at 67fps.
Today's DirectX 11 games are only brushing the surface of Microsoft's new interface, and we can expect it'll be some time before we'll see precisely how well the newest cards can handle a full DX11 experience.
Of course the Sapphire Radeon HD 5970 also supports Eyefinity, allowing you to easily use up to three screens to stretch your games panoramically. This promises a fantastically immersive experience, and no other single card is better equipped to handle the demanding needs of such huge resolutions.
NEXT: our expert verdict >>