AMD Radeon HD 6850 review

The ATI Radeon HD 5850 was a high-end part that debuted at £173 exc VAT. Despite winning awards, AMD believes it was something of an aberration, too expensive for most consumers despite its excellent benchmark results. Thus, at just £127 exc VAT, the new HD 6850 marks a return to the all-important “sweet spot”.

It’s not just cheaper than last year’s model; it also features a redesigned and optimised architecture. The main change concerns the arrangement of stream processors. While the HD 5800 cards had a single complex processor with four simple “slave” shaders, AMD has done away with slave shaders entirely and instead packaged a quartet of complex cores together.

While this means the HD 6850 has only 960 stream processors compared to the 1,600 of the HD 5850, each quartet can handle more complex tasks in a more efficient manner. It’s a change that AMD hopes will allow its cards to do more with less.

The rest of the HD 6850 is conventional, with 1.7 billion transistors – 400 million fewer than the HD 5850 – and a 775MHz core clock. One gigabyte of GDDR5 RAM runs at 1,000MHz, and there’s a 256-bit memory bus.

These refinements made for some interesting results in our Crysis benchmarks. An average of 33fps in our 1,920 x 1,080 Very High benchmark is four frames faster than the Nvidia’s 1GB GeForce GTX 460; that gap remained when we activated 4x anti-aliasing, with a score of 29fps just about playable.

The HD 6850 scored 35fps in our High quality test at a higher resolution of 2,560 x 1,600, although that was the limit; when we loaded the same test at Crysis’ highest settings, the HD 6850 struggled to a score of 21fps.

Its Nvidia rivals were slightly ahead in our DiRT 2 tests, however. The GTX 460 ran through our maximum-quality benchmark at 1,920 x 1,080 at more than 60fps, with the HD 6850 returning 53fps.

There’s little to worry about when it comes to heat and power consumption, either. A maximum temperature of 83 degrees isn’t too high, and a peak power draw of 248W in our test rig is significantly lower than Nvidia’s equivalents.

The final piece of AMD’s mid-range puzzle is the price, and it’s the card’s greatest strength. At £127 exc VAT the HD 6850 is the same price yet faster in most tests than the GTX 460. And when compared to AMD’s own HD 6870, the small loss in frame rates is easily made up for by the price saving of nearly £50. It’s a little unusual in that the HD 6850 is slower than its predecessor, but the price means it’s undoubtedly the finest mid-range card available.