Labs

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Athlon 64 X2s make up most of AMD's processors line-up. They range in speed from 2.2GHz up to 3.4GHz, and we've tested all the models on the market that AMD currently produces. However, make sure you check the part code when buying any of these processors, as some retailers may still be selling older versions with subtly different specifications.

All the current Athlon 64 X2 processors use the AM2 processor socket. Because of this they have an array of delicate pins on the underside of the processor. This makes them more vulnerable to damage than Intel's LGA775 processors, so you should handle them with the utmost care.

All Athlon 64 X2 processors have two processing cores. Each core has its own 128KB L1 cache, twice the size of those on Intel's processors. This means the core can access more data and instructions at high speed. However, Athlon 64 X2 processors also use separate L2 caches for each core. This means that commonly accessed information must be duplicated across both caches, which is less efficient than Intel's shared cache approach.

While Intel processors use a memory controller on the motherboard, AMD processors have one built into the processor itself. This should speed

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up memory access by eliminating a potential bottleneck, and the 2,000MHz external bus speed is certainly impressive. However, this system locks the processor to using a particular type of memory, and so Athlon 64 X2 chips are compatible with only DDR2 memory.

Different ranges

All the processors from the 4200+ up to the 5200+ use the Brisbane core. This is manufactured using a 65nm process, which should make these processors fairly power efficient. However, Athlon 64 X2 processors use higher clock speeds to achieve the same results as Intel processors, and in doing so they use more power and generate more heat.

Each core has its own 512KB cache, which makes a total of 1,024KB. However, the larger L1 caches, quicker memory access and separate cache design make it hard to compare the processors directly with Intel's.

The faster processors in the range, starting with the 5600+, are based on the older Windsor core. This uses a 90nm manufacturing process, which means that these processors tend to run hotter and use more power than most others here. These processors also have larger L2 caches, with 1,024KB per core.

Specific processors

All the AMD Athlon 64 X2 processors that are based on a Brisbane core offer good value, and the 4200+ is particularly outstanding. The Athlon 64 X2 5000+ Black Edition is a good choice if you plan to overclock your processor. Like Intel's Extreme processors, it has an unlocked multiplier, which makes overclocking easier. However, unlike the Extreme processors it isn't ridiculously expensive and costs just £69 including VAT - the same price as the standard 5000+.

Unless you want to upgrade an AM2-based computer, the Windsor-core processors offer very little to get excited about. Each processor is surpassed in our overall benchmarks by an Intel processor of a similar price. Even if you are upgrading an older PC, you should be wary of spending a large amount of money for relatively modest performance gains.