It's expensive, but this is easily the most powerful single-GPU graphics card we've seen
The Radeon HD 7970, codenamed Tahiti, is the first of AMD’s next generation of graphics cards. It has several improvements over last year’s top-end HD 6970, namely a new, more power-efficient 28nm process, 2,048 compared to 1,536 stream processors and 3GB of GDDR5 memory with a 384-bit interface, compared to 2GB and a 256-bit interface on last year’s model.
Not that it particularly matters when it’s in your PC, but the HD 7970 is a smart-looking card. Our reference AMD model has a glossy finish and a heatsink that tapers off towards the rear of the card – making it look like less of a slab than AMD’s previous high-end cards. AMD has redesigned the card’s fan to make it more efficient and quieter, and the card is certainly quiet at idle and makes only a low hum under load. It also turns off most of its circuitry when your screen is off – even the fan stops running. Our test PC’s power consumption dropped from 73W to 54W when the screen was off, compared to no change with the HD 6970.
There have also been some changes to the card’s ports configuration. Instead of the HD 6970’s two DVI, two DisplayPort and one HDMI ports, the HD 7970 only has one DVI alongside its HDMI and DisplayPort sockets. The loss of the DVI port means the cooling slot can be the full width of the card to better channel heat out the back of the case. AMD ships an HDMI to DVI converter and an active Mini DisplayPort to DVI adaptor with the card, so you shouldn’t have to invest in monitors with DisplayPort adaptors for Eyefinity triple-monitor gaming. Using the included adaptors you could have three DVI monitors, two DVI and an HDMI, one DVI, one HDMI and one DisplayPort and so on.
The card’s memory runs at the same 1,375MHz speed as the HD 6970’s, but the clock speed has increased from 880MHz to 925MHz. This is a modest speed boost, so the card’s main performance increase comes from its extra 512 stream processors, and they certainly make a difference – this is easily the fastest single-GPU card we’ve seen. The HD 7970 managed 88fps in our Dirt 3 test at 1,920×1,080 with Ultra detail and 4x anti-aliasing, and even when we ran the benchmark on three monitors in Eyefinity mode we still saw a smooth 41.5fps – the HD 6970 could only manage 31.1fps in the same test, with a jerky 26.1fps in places.
It was in the punishing Crysis 2 test that the HD 7970 really shone. At 1,920×1,080 and detail levels set to Ultra for all the fancy DirectX 11 tessellation effects, we still saw a smooth 41.4fps. In contrast, the HD 6970 could only manage 28.5fps, which is barely playable at such high detail levels. It’s also ahead of its main rival from Nvidia, the GeForce GTX 580, which managed 32.8fps in the same test. The only cards we’ve seen with a better score in Crysis 2 are the dual-GPU Radeon HD 6990 and Nvidia GeForce GTX 590, both of which are nearly £600 and are very power hungry; when fitted with the HD 6990 and GTX 580 our test PC drew a huge 355W and 388W under load, compared to 236W with the HD 7970.
Next page: overclocking and verdict
|Interface||PCI Express x16|
|Slots taken up||2|
|Graphics Processor||AMD Radeon HD 7970|
|GPU clock speed||925MHz|
|Architecture||2048 stream processors|
|Power leads required||1x 6-pin PCI Express, 1x 8-pin PCI Express|
|Accessories||HDMI to DVI, active mini-DisplayPort to DVI adaptors|