AMD Radeon HD 6970 review

AMD introduced its latest series of graphics cards a month ago with its mid-range HD 6800-series. That was enough to cause Nvidia to rush out the GTX 570 to market, and now AMD is following up with its single-chip flagship cards, the Radeon HD 6970 reviewed here, and the HD 6950.

It's certainly got the specification to go head-to-head with Nvidia's finest. The 40nm chip, code-named Cayman, packs in an 880MHz core clock alongside 2GB of GDDR5 memory running at 1,350MHz. The 389mm² die includes 2.64 billion transistors, and the core provides 1,536 stream processors – an impressive figure, but slightly less than the number included on the HD 5870, the firm's previous top-end card.

That sounds like a retrograde step, but it's indicative of the major changes introduced by AMD in its latest architecture. Previous cards used a single powerful stream processor surrounded by four slave chips, but this year's models do away with this structure, instead using four equally powerful stream processors in each package.

Fewer stream processors are used, but the resulting chip is more efficient and powerful than its predecessors. AMD has divided its stream processors into two overarching graphics engines, with 24 packages, each containing 64 processors across the card.

AMD’s revised architecture proved its worth in our Crysis benchmarks. The Radeon HD 6970 ran through our 1,920 x 1,080 Very High quality test at 48fps, with this score falling to 42fps and then 38fps when we enabled 4x and 8x anti-aliasing. AMD’s card even ran through our Very High test at the huge resolution of 2,560 x 1,600 with a playable score of 31fps, although adding anti-aliasing dropped this to 25fps.

These scores indicate that the Radeon HD 6970 will handle any game you care to throw at it, but the situation is less clear-cut when you consider Nvidia’s cards. The GTX 580 retains its crown as the fastest single-GPU product on the market, but it’s the GTX 570 that AMD should be worrying about. Nvidia’s card is around the same price as the HD 6970 and almost as impressive in our tests, running only 2fps slower than the HD 6970 in our 1,920 x 1,080 Very High quality test with 4x anti-aliasing activated.

For our secondary gaming test, we’re moving to Just Cause 2 as of this month – a keen test for any graphics card thanks to its detailed environments, complex lighting effects and long draw distances. The Radeon HD 6970 motored through its Very High quality tests (run at 1,920 x 1,080 and with 8x anti-aliasing) at 37fps, but again the GTX 570 was better, romping through the same tests with an average of 63fps.

Elsewhere, AMD has introduced a vapour chamber cooler in the Radeon HD 6970, aping Nvidia’s GTX cards. It works by circulating liquid around the chip to transfer heat away from the surface, and makes the HD 6970 a very large card indeed. At 274mm in length, it’s a shade longer than the GTX 580, and requires both eight- and six-pin power plugs.

Unfortunately, AMD’s vapour chamber isn’t as efficient as Nvidia’s. An idle temperature of 57˚C is fine, but the HD 6970 rocketed to 92˚C during our stress tests – 8˚C hotter than the GTX 570. It’s power intensive, too: our test rig drew 377W with the card under stress; with the GTX 570 it drew 283W; and with the GTX 580 in situ it pulled a total of 292W. It's also loud, especially during more intensive benchmarks.

Overall, the AMD Radeon HD 6970 is impressive, but it doesn’t quite do enough to take over from Nvidia at the graphics card top table. The price is too similar to the GTX 570, the noise levels higher, efficiency lower and overall performance slower. AMD needs to do better than this to grab its crown back.

Author: Mike Jennings