AMD's top rank of CPUs is just reaching its first birthday, and what better way to celebrate than by clocking up the most attractive price-to-performance ratio of any current processor family.

It's a wide-reaching range based on the K10 architecture, tripling the old Phenom's L3 cache to 6MB and reducing die size to a modern 45nm. And it runs from an almost-budget $100 up to the still affordable top-end $260.

Quad core

This is where the big guns of AMD's processor line-up show their worth: the quad-core Phenom II X4 parts offer excellent performance for the money. The top-end X4 965 is even multiplier-unlocked, and has recently seen its TDP lowered from 140W to 125W (so make sure you buy one of the latest batch).

That's still pretty high - the Phenom II can't claim to be the most efficient high-end CPU around - but it's similar to Intel's hottest models.

In our benchmarks, the X4 965 scored 1.91, despite costing only around $260. To put that into perspective, the nearest Intel price-equivalent would be a Core 2 Quad Q9400, which managed just 1.61 in our tests for the only slightly cheaper $229.

In fact, you'll need to pay close to $1000 to get an Intel CPU that can match the X4 965 for overall speed, and it certainly won't be one that fits in a low-cost motherboard, as these AM3 parts do.

The rest of the range is impressive too, with even the relatively expensive $185 Socket AM2+ X4 945 scoring 1.76 - almost identical to Intel's $500 Core 2 Quad Q9650.

All four X4s are attractive economically, but we'd recommend paying the small premium for the X4 965, if only for the extra leeway its unlocked multiplier will afford you in the long-run.

Triple core

Just one standard triple-core Phenom II was available at the time of writing - the 2.8GHz X3 720 - but a 2.6GHz X3 710 should also be available by the end of January.

These models don't quite replicate the appeal of their Athlon II X3 cousins - despite higher frequencies they're a tad slower overall, but to compensate they also cost a fair bit less. So it's a question of budget: if $185 for an AM3 X4 sounds too dear, the $158 X3 720 is a viable alternative and quicker than a quad-core Athlon II.

Dual core

While the Athlon II X2s employ a native dual-core design, the Phenom II X2 line is from the same stock as the X3 and X4, with the extra cores simply disabled. These chips therefore keep the same 512KB L2 cache per core and 6MB shared L3 cache - but they only manage to lower the TDP to 80W, rather than the 65W of the Athlon II X2.

While they perform well, they don't offer the appeal of the dual-core Athlons. The Phenom II X2 545 scored 1.49 for its $100 price; compare that to 1.54 from a cheaper Athlon II X3 435 and it seems the extra core of the Athlon has the edge.

The increased TDP also works against the Phenom II, so we'd stick to the triple- and quad-core models for now.

CPU ratings: Click on box for larger size