Richard Sapp: Review: AMD Radeon HD 6970

Finally they've arrived; the much-anticipated Cayman GPU-powered HD 6900 series cards from AMD. And right here we've got the very top-end of AMD's latest single-GPU cards, the AMD Radeon HD 6970.

Now we've been waiting a fair few months for the release of these new cards, with their brand spanking new GPU, and still it's hard to see exactly why we've been waiting so long.

Originally penned in for launch just after the HD 6800 cards, suddenly we saw the launch slip back and Nvidia then spoiling a party that simply didn't exist. The Nvidia GeForce GTX 580 was brought out incredibly early, specifically to counter these Cayman-powered cards only to find they were still some months away from release.

AMD has remained fairly tight-lipped about the slippage. Some of our sources claimed it was simply down to money. AMD wanted the higher margins of the mid-range HD 6800 cards around Thanksgiving aiding its bottom line, whereas a few top-end HD 6900 cards wouldn't have given them the same cash boost.

Still, I'm sure there were a fair few people who held off buying a new card until AMD had its top-end GPUs out the door, so I'm not entirely convinced about that rumour.

At a recent briefing, though, AMD blamed the PowerTune technology in its new cards as the delaying factor. But to us that sounds suspiciously similar to Nvidia blaming the delay of the GTX 480 on the design of its Tessellation engine.

It may well be a while before we know the full story.

AMD radeon hd 6970

Beyond the dual-graphics engine at the frontend, the chip we're seeing still has the same essential makeup as the Cypress-powered Radeon HD 5800 series. But the doubling up of the graphics engine in the Cayman GPU is most definitely important.

In terms of AMD's latest graphics cards, the Radeon HD 6970's DirectX 11 performance boost over the older DX11 cards, such as the Radeon HD 5870 and Radeon HD 5850, is seemingly all down to this dual-graphics technology. Instead of having a single engine frontend, and therefore a single tessellation chip funnelling all the work out to the various SIMD engines beyond it, there are now two working concurrently.

This means the card's not getting so bottlenecked with tessellation-heavy calculations when DirectX 11 games are put through their paces.

The AMD Radeon HD 6970 shows this extra performance, especially in its Unigine Heaven benchmark numbers. It comes in at nearly 70 per cent faster than the Radeon HD 5870, which is a fairly impressive improvement.

With the slightly larger die, AMD has been able to jam on a few more SIMD engines; a total of 24 against the Cypress maximum of 20. Coupled with slightly higher clockspeeds, that helps push the newer card past its increasingly obsolete brethren.

Within those SIMD engines, the unified shader architecture has also been redesigned. AMD's stream processors have remained largely unchanged since the RV770/HD 4800 days, with four fixed-function streaming cores and one more complex special function core. This has been refined into just four stream processing units with mostly equal functionality.

The result of this is that each of the unified shaders should be able to offer the same sort of performance with a smaller footprint and simplified scheduling of tasks.

Both the new Radeon HD 6970 and the Radeon HD 6950 also come with a rather bulging frame buffer too. With 2GB GDDR5 graphics memory on board, these cards are designed to be at home at higher resolutions or with increased anti-aliasing prowess, or indeed both.

On the anti-aliasing front, there have also been further advances. With the latest Catalyst Control Suite offering up a new setting called Enhanced Quality Anti-Aliasing (EQAA). This apparently offers "enhanced smoothing of aliased edges without requiring additional video memory, and with minimal performance cost".

The minimal performance cost is most definitely true; in DiRT 2 we saw a drop of a single frame per second across the benchmark. As for a tangible graphical enhancement though, well, that's harder to quantify. It's possible we're not looking in the right places, but on lower resolution settings, where AA is more important, I couldn't notice any difference no matter how hard I looked, and we think the average gamer will struggle, too.

As for the proposed reason for the Radeon HD 6900 delays, the new PowerTune technology, again we're talking about a fairly intangible enhancement. And, for us, probably not something worth delaying the launch of a new range of cards over?

So what is it? It's power management tech designed to dynamically shift around the GPU core clock depending on the thermal limits of the card design. Essentially dropping the clockspeed when it can get away with it and upping it when it can't.

This enables the GPU to stay below the thermal envelope that would ordinarily result in permanently throttled performance in intensive applications.

But what we really care about is performance, isn't it? So how does the HD 6970's new GPU stack up in that department then?

AMD radeon hd 6970

Nvidia's sub-�300 GTX 570 is the yardstick by which the HD 6970 is going to be tested and, aside from the Metro 2033 scores and a few extra FPS in the AvP benchmark, the AMD card struggles to keep pace with the cheaper chip.

The other bad news is that the HD 6950, which is still largely comparative to the GTX 570 is also much cheaper than its big brother.

All these benchmarks were taken at 2560 x 1600, with 4x anti-aliasing. Our basic test bench remains an Intel Core i7-930 at 2.8GHz, Asus P6X58D-E motherboard and 6GB Corsair DDR3 at 1333MHz.

DirectX 11 Tessellation performance

Heaven: FPS ? higher is better

HD 6970 ? 21.7
HD 6950 ? 19.5
GTX 570 ? 22

DirectX 11 Gaming performance

Metro 2033: FPS ? higher is better

HD 6970 ? 13
HD 6950 ? 12
GTX 570 ? 3

DiRT 2: FPS ? higher is better

HD 6970 ? 55
HD 6950 ? 51
GTX 570 ? 64

Lost Planet 2: FPS ? higher is better

HD 6970 ? 25
HD 6950 ? 23
GTX 570 ? 32

Aliens vs Predator: FPS ? higher is better

HD 6970 ? 25
HD 6950 ? 22
GTX 570 ? 22

DirectX 10 gaming performance

Just Cause 2: FPS ? higher is better

HD 6970 ? 30
HD 6950 ? 27
GTX 570 - 30

Crysis Warhead: FPS ? higher is better

HD 6970 ? 20
HD 6950 ? 18
GTX 570 ? 25

Far Cry 2: FPS ? higher is better

HD 6970 ? 65
HD 6950 ? 60
GTX 570 ? 66

AMD radeon hd 6970

So the AMD Radeon HD 6970 is new, it's got loads of graphics memory and some tweaked GPU design, so how does it perform?

In gaming terms we'd say it performs almost exactly like the beefed-up Cypress GPU it's replacing, but with a few fairly notable exceptions.

The key improvements in the Radeon HD 6970 over the Radeon HD 5870 all occur, unsurprisingly, at the DirectX 11 level.

As we mentioned before, that's most evident in particularly tessellation-heavy benchmarks, such as Heaven, and also the system-taxing Metro 2033. With its tessellated character models, Metro 2033 can bring a gaming rig to its knees, and the HD 5870 could barely run the benchmark at 1680 x 1050, let alone at 2560 x 1600.

Although, the AMD HD 6970 gives decent performance scores at both settings and, importantly for AMD, is four times as fast as Nvidia's GeForce GTX 570 in Metro 2033 at the top resolution.

And this is really key to the HD 6970's success or lack thereof ? how does it stack up against its Nvidia-coloured competition?

As well as the Metro 2033 score, the Aliens vs Predator benchmark too makes good reading for the AMD faithful. It may only be by a few frames per second, but the fact that it's again faster than the competing GTX 570 is important.

Unfortunately for AMD, that's largely where the good news ends. It's very close across the rest of our benchmarking suite, but the Nvidia GeForce GTX 570 has the lead in all but those two DirectX 11 titles.

Even in Heaven the GTX 570 has the lead, albeit by a very, very narrow margin.

So the AMD HD 6970 is trading blows with the GTX 570, which in itself is a very good card. Unfortunately it's also a cheaper card, which to all intents and purposes scuppers the HD 6970 at birth.

The other issue here though is the GTX 570 is only a very slight redesign of the GTX 480's GPU, offering very close performance scores. The Radeon HD 6970 then is only just about keeping pace with Nvidia's top card of the last generation.

Hardly something to really go shouting from the rooftops in this competitive graphics card market.

The �400+ GTX 580 though is still by far the faster card, and holds on to its 'fastest single-GPU' title. There's little point comparing the HD 6970 with Nvidia's fastest though as this AMD offering is aimed at a very different market segment.

In this era of improved multi-GPU performance though the top-end AMD GPU is also facing off against the cheaper SLI pairing of twin GTX 460 1GB cards. And unless you're only looking at the Metro 2033 benchmark at 2560 x 1600, the HD 6970 loses out across the board.

The usual power/motherboard caveats apply here, but if you've got a compatible mobo and a hefty-enough PSU then it's still tough to look past this SLI setup.

The other fly in the Radeon HD 6970's ointment is the other Cayman-powered card released alongside it; the Radeon HD 6950. Unlike the Radeon HD 6870 and HD 6850 there is little tangible difference in the performance of these two cards.

Across our benchmarking suite you're looking at a maximum differential of 8fps, and that's on DiRT 2 where we're getting 85fps and 77fps respectively. At that speed you're hardly likely to really notice an 8fps drop off.

With the HD 6950 so much cheaper than its big brother that's where the sensible money's going out of the two. In performance terms, too, it sits somewhere between the GTX 470 and the GTX 570, making it much more of the value proposition.

If there were only AMD GPUs populating the world then we would be heralding the HD 6970's numbers as bringing the sort of single-GPU performance we'd never before seen. As it is we did that in March when the GTX 480 was released?

We liked

The speed boost over the previous generation's HD 5870 is impressive and shows the improvements of the AMD architecture, specifically at DirectX 11 gaming benchmarks.

We disliked

The big problem again for AMD is the fact that Nvidia has already brought out a faster single-GPU card that beats it hands down in the GTX 580. There's also the GTX 570 as another spoiler card, which has forced AMD to bring the HD 6970 out at a cheaper price than it wanted and still has a few FPS over it in performance terms.

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