AMD Radeon HD 7970 3 GB

The Radeon HD 7970 uses AMD’s Southern Islands GPU architecture for the first time. The prospect is mouthwatering, combined as it is with the 28nm engraving, implementation of PCIe 3.0 and DirectX 11.1 compatibility, all for the first time. The 7970 also has much improved 2D energy consumption, 3 GB of GDDR5 memory and no fewer than 2048 processing units. There’s a clear break with the Radeon HD 6000 generation.

Size, noise and heat generation

There’s little new to report when it comes to the size of the card. It’s of standard length for this range (27.5 cm) and there’s a double-decker AMD heatsink. The hot air is mainly expelled from the chassis and once again there’s a vapour chamber radiator (6th gen).

The noise levels generated by the fan are more or less in line with the Radeon HD 6970: pretty low at idle and extremely loud during gaming. During 3D gaming, it’s particularly annoying for anyone sitting in the vicinity – and perhaps watching television – especially as the fan tends to speed up and down, constantly alternating rotation speed.

Energy consumption

On introducing the Radeon HD 7970, AMD had plenty to say in praise of its low energy consumption. ZeroCore Power technology is now included and allows you to reduce energy consumption at idle by up to 24% by deactivating several of the card’s processing units. From 100 Watts with the Radeon HD 6970 we’re now down to 85 Watts on our test machine. Better still, when the screen is off, energy consumption drops even lower to 74 Watts, which is excellent, especially on a high-end model.

During gaming we took a reading of 407 Watts at the socket (the whole machine). This is only a little more than the 6970, but is a lot better than the GeForce GTX 580 which consumes 431 Watts under the same conditions. Given the increased level of performance (see below), it looks as if AMD has put the reduction in engraving thickness to good use. In absolute terms however, energy consumption remains high.

ZeroCore Power also manages noise well in 2D. When the screen goes into standby mode and the computer is still on, the fan stops running altogether. The graphics card then hardly heats up at all (the GPU is almost switched off). With a similar principle in mind, when in a CrossFire X configuration, the various additional cards are entirely switched off when not in use for gaming, making for a better optimised system both in terms of noise and energy consumption.

Gaming performance

The graphics chip (codename Tahiti) greatly improves the Radeon HD 7970's capacities in comparison to the previous generation. The difference on average with the 6970 is 37%, which is a great improvement, thankfully allowing AMD to overtake the GeForce GTX580 (+12%) at last. However the Radeon HD 6990 (double GPU) remains quite some way out of reach (+20%). A CrossFire X system with the Radeon HD 6950 or HD 6970 therefore still gives superior performance even though energy consumption is then higher, as are the noise levels.

General performance average
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This card is also the first graphics card to implement the PCI-Express 3.0 (PCIe 3.0) interface and the first DirectX 11.1 compatible card. Backwards compatibility means that the Radeon HD 7970 functions perfectly on PCIe 2.0 motherboards. What's more, we didn't note any difference between use in PCIe 3.0 and PCIe 2.0 modes.
DirectX 11.1 will only be available on release of Windows 8 (end 2012). Games using this instruction set will therefore also have to wait until then.

While this is certainly the ideal solution for playing Battlefield 3 with all settings pushed to max and antialiasing on, it’s doubtful that AMD will stay at the top of the tree for long. In addition, what with the HD 7970's rather high launch price (£450), it may well be wiser to wait for the Nvidia Kepler generation, before raiding the piggy bank.

Consult the performance index table