For a chip that trades on efficiency, the AMD Phenom II X4 905E's results in our platform power consumption tests are ugly. Using optimised motherboard settings, it actually consumes more power than the Phenom II X4 965 Black Edition.

Something is clearly not right. Very likely, it's a problem related to voltage settings and our test board's BIOS. Anyway, two obvious lessons come out of this. Firstly, full motherboard support is required to get the best out of these low-power processors. Secondly, you may have to jump into the BIOS and do some hand tuning of the voltage settings.

As it is, we can't comment on the 905E's low power credentials. However, what we can say is that it runs an awful lot cooler than a normal quad-core Phenom II processor, even with the wrong voltage settings.

In most other areas, the 905E's performance is predictable, which is to say solid if hardly spectacular. Compared to a budget quad-core chip but one that is nevertheless clocked slightly higher, such as the Ahtlon II X4 620, the 905E trades punches across our benchmark suite. It's a little slower for video encoding but quicker at professional 3D rendering, gaming and file decompression.

As for the inevitable comparison with its low-power stable mate, the Athlon II X4 610E, it knocks out around 25 per cent more frames per second in the World of Conflict game benchmark. That could be the difference between smooth gameplay and irritating stutters. The 905E also clocks up better than the 610E, hitting 3.9GHz.

We liked:

Thanks to problems with motherboard support, the Phenom II X4 905E had a hard time impressing us. However, we still like the idea of a quad-core processor optimised for power efficiency. In raw performance terms, this chip would certainly make for great small form factor system.

We disliked:

Judging the Phenom II X4 905E's power consumption is tricky without proper motherboard support. However, we're confident that it's less efficient than the Athlon II X4 610E and that makes it tricky to recommend given the price premium. We'd go with the cheaper chip.

Verdict:

An interesting take on low-power performance, but less convincing than the Athlon II X4 610E.

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