AMD Fusion review

Combining a CPU and GPU onto one silicon die is a concept AMD pioneered back in 2007, to enable more efficient processing while reducing size, power consumption and manufacturing costs. Fast-forward to 2011 and Intel’s Sandy Bridge processors have been offering on-die graphics since January, yet Fusion is only just coming to fruition. Not for the first time, AMD finds itself playing catch-up.

Initially at least, AMD Fusion isn’t a direct competitor to Sandy Bridge. The first Fusion chips are based around the new 40nm Bobcat core, aimed squarely at the low-power roles dominated by Intel’s Atom processors. This platform is codenamed Brazos, and it includes both single- and dual-core processors, in two flavours: the regular E series (codenamed Zacate) and ultra low-power C series (Ontario).

The new chips all boast one of two Radeon-branded GPUs (identical but for clock frequency) with 80 DirectX 11 stream processors, plus AMD’s Unified Video Decoder 3 for high-definition media. That means that even the low-power C series should handle complex 3D animations and Blu-ray media. AMD is also fully supporting OpenCL and Microsoft’s DirectCompute framework, encouraging programmers to use the GPU to accelerate general-purpose calculations. For this reason, AMD likes to refer to Fusion chips as APUs – accelerated processing units.

Overall, the Brazos formula is similar to Nvidia’s Ion platform, which marries an Intel Atom CPU to a discrete Nvidia GPU. The difference is that, for obvious reasons, Ion can’t reap the efficiency benefits of combining everything on one die — potentially giving AMD an unanswerable advantage.

Putting Brazos to the test

Since Brazos is aimed primarily at consumer devices such as netbooks and tablets, the chips are mounted directly on the motherboard, rather than socketed. That means you can’t buy a Brazos processor on its own; but if you want to build a home media centre, or a compact desktop PC, several manufacturers offer mini-ITX motherboards with integrated processors at around the £100 mark. We tested Gigabyte’s E350N-USB3 motherboard package, which has the top-end E-350 processor, with support from 2GB of 1,066MHz DDR3 RAM (the board supports up to 8GB of RAM in two DIMM sockets) and a low-power 2TB Seagate Barracuda LP hard disk.

The results were decent, but not stellar. In our application benchmarks, the Brazos system achieved an overall score of 0.53 — higher than any Atom- or Ion-based system we’ve seen, but not by a wide margin. For comparison, our A-Listed netbook, the Asus Eee PC 1001P, achieved an overall score of 0.39, while the Ion-powered Zotac Zbox HD-ID34 managed 0.46.

When it came to media playback, the E-350 had no difficulty rendering video at resolutions up to 1080p in a variety of formats – including high bit-rate Blu-ray rips and streaming video from YouTube HD. Windows Media Center felt responsive, but we noted that CPU usage was around 70% whenever video was playing, and performing more or less any background action caused stuttering. Considering the platform includes a built-in hardware video decoder, we’d expected better: hopefully a future driver upgrade will improve matters.