AMD Fusion for desktops review

AMD’s new A-Series chips (codenamed “Llano”) are its first mainstream range of so-called APUs – “accelerated processing units” which combine CPU and GPU components in a single chip. We’ve already road-tested the mobile models; now we have the first desktop parts. The quad-core A6-3650 and A8-3850 head up the mainstream A6 range and the high-end A8 series, with lesser models to follow. There’ll also be a lightweight dual-core A4 series, as the table below shows.

Processing power
As with their mobile counterparts, the CPU logic in the new chips is based on the 32nm Phenom II design, originally unveiled in 2008. AMD has removed the L3 cache, however, and kept clock speeds low: while the still-available Phenom II 970 runs at 3.7GHz, the A6-3650 strolls along at 2.6GHz. Even the flagship A8-3850 only hits 2.9GHz. And there’s no Turbo Core feature on these models to push the frequencies higher: lesser A6 and A8 processors will offer dynamic overclocking, but won’t go any faster than these chips.

In terms of processing grunt, this leaves the A-Series some way behind Intel’s storming Sandy Bridge chips. In our Real World Benchmarks the top-end A8-3850, partnered with 4GB of RAM, achieved an overall score of 0.67 – well below even the lowly Core i3-2100, which scored 0.79. The mid-range A6-3650 managed 0.64, a score on par with a low-end dual-core Athlon II.

That doesn’t necessarily mean A-Series processors will feel sluggish. Both chips achieved their best scores in our Responsiveness test, managing 0.75 and 0.73 respectively. Multitasking scores of 0.59 and 0.56 were, however, disappointing for quad-core processors – the result, we suspect, of the lack of L3 cache. If you want an AMD chip to truly compete with the Core i7, you’ll have to wait for the forthcoming Bulldozer architecture, due later this year in CPU format and early next year as an APU.

Graphical capabilities
Desktop performance is only half of the Fusion formula. Inside every A-Series processor you’ll also find a Radeon-branded DirectX 11 GPU. A6 processors enjoy 320 shaders running at 443MHz, while A8 models bump this up to 400 shaders at 600MHz.

This is an impressive amount of graphical power. The A6-3650 romped through our Low-quality Crysis test at an average of 53fps at 1,366 x 768, and kept up a playable 31fps at 1080p. The A8-3850 nudged up to 55fps and 34fps. Even when we stepped up to Medium detail, the game remained playable at 1,366 x 768, with the A8 averaging 34fps and the A6 hitting 30fps.