Protech Review: AMD Radeon HD 7970 Review

Verdict

Fantastic performance, although the sky-high price puts this out of reach for most

Review Date: 26 Jan 2012

Reviewed By: Mike Jennings

Price when reviewed: £360 (£432 inc VAT)

AMD might be having a tough time of it on the CPU front, but when it comes to graphics cards it's just taken a leap ahead of the competition. Its new single-GPU flagship - the Radeon HD 7970 - is the first to use a 28nm manufacturing process, and beats its major rival Nvidia to the punch.

The impact of the new process is significant: the HD 7970 die is 378mm² compared to the 389mm² size of its predecessor, the Radeon HD 6970, and AMD crams in 4.3 billion transistors - a huge bump up over the 2.6 billion included in last year's top-end single GPU. The HD 7970 compares favourably to Nvidia's GeForce GTX 580, too, which includes 3 billion transistors in a 520mm² package.

AMD has also given its Very Long Instruction Word 4 (VLIW4) architecture the boot, deeming its bottlenecked parallel performance a hindrance. While VLIW4 cores and their schedulers proved adept at handling groups of identical operations concurrently, they struggled with varied groups of tasks required by more complex applications and games. Some tasks were scheduled and processed promptly but, often, the scheduler couldn't keep up, with instructions left behind and bottlenecks caused in the GPU.

It's a big change. VLIW-based architectures, including VLIW4, have been used in AMD graphics cards since the Radeon 9700's introduction in 2002. Instead, the new card uses multiple instruction multiple data cores (MIMD). These are constructed from several single-instruction multiple data cores (SIMD) grouped together, and are capable of more efficiently handling a more diverse range of tasks, as well as making dynamic changes to the compute schedule - something VLIW4 couldn't do.

Each MIMD package is made from 64 SIMD cores, and each package has its own L1 cache, with L2 cache and memory controllers shared between several packages. AMD has given these cores their own name, too, with the marketing department swooping into action to dub each unit a Graphics Core Next.

The HD 7970 itself includes 2,048 SIMD cores inside 32 MIMD clusters, which is more than the 1,536 stream processors used in the HD 6970. The core clock is 925MHz, there's 3GB of GDDR5 RAM running at 1,375MHz, and the memory bus is 384-bits wide. The latter is an improvement on the 256-bit bus of last year's cards, and on a par with the GTX 580.

In our 1,920 x 1,080 Very High quality Crysis test, the HD 7970 scored 65fps: 11fps faster than the single GPU GTX 580, 17fps quicker than the HD 6970, and only 2fps short of the dual-GPU Radeon HD 6990. Adding 4x anti-aliasing saw the HD 7970 score 59fps - still 11 frames better than the Nvidia card - and running the game at 2,560 x 1,600 returned a 43fps result, 15fps more than the GTX 580 could manage.

An average of 76fps in Just Cause 2's highest settings at 1,920 x 1,080 and with 8x anti-aliasing is 2fps quicker than the GTX 580 and more than twice the speed of the HD 6970. It's an adept overclocker, too: we boosted the core and memory clocks to 1,100MHz and 1,500MHz and found the 43fps score in our toughest Crysis test rose to 49fps.

The HD 7970 hit a reasonable 79 degrees during our tests, but its peak power draw of 394W in our test rig is more than the 292W pull of the GTX 580 and the 377W draw of the HD 6970. It's louder than the Nvidia card, too, although we anticipate board partners will release cards with quieter coolers.

You'll also have to make sure your PC is man enough to handle the new card. It's 281mm long and dual-height, and needs both eight-pin and a six-pin power adapters. The backplate now has just one DVI-I output alongside the single HDMI and two mini-DisplayPort sockets, with more room given over to pumping out hot air.

There's an elephant in the room, though: an eye-watering expected price of £432 inc VAT (UK street prices have yet to be confirmed). Nvidia's GTX 580 can be had for much less than £400, and the Radeon HD 6970 is cheaper still at less than £250. They're both slower, but both will handle games at 1,920 x 1,080 without breaking a sweat.

That puts the HD 7970 beyond all but the wealthiest of enthusiasts, and its astonishing performance means you'll need to be running a 30in screen or multiple monitors to truly make use of all the horsepower on offer. However, the new technology will soon trickle down to more affordable models, and when that happens we'll be first in line.

Author: Mike Jennings