Verdict: The Q6600 is one of the best CPUs ever made.

Intel just managed to sneak a sample of the UK's first Core 2 Quad Q6600 into last year's CPU megatest, and since then it has added another model to the Core 2 Quad series.

This chip is known as the Q6700 and runs at 2.66GHz. However, this is not to be confused with the Core 2 Extreme QX6700, which is also clocked at 2.66GHz, as the latter has a fully unlocked multiplier, so it's great for overclocking, while the multiplier on the Q6700 is locked upwards (it can be lowered). The Core 2 Quads are quad-core CPUs, but unlike the AMD Phenom, they comprise two dual-core dies sandwiched together on one package. This means that each pair of cores shares a 4MB Level 2 cache, although none of the cores can access the entire 8MB of Level 2 cache. The Q6600 is clocked at 2.4GHz, and is available in two steppings - B3 and G0. Both steppings perform identically, but G0 chips run considerably cooler, and can typically be overclocked a good 300MHz more than B3 chips. Many retailers charge more for a G0 stepping Q6600, but if you plan to overclock then it's worth paying the £5-10 surcharge.

The Q6600 is priced very similarly to the 2.2GHz Phenom 9500, but it proved to be significantly faster in every benchmark we ran on the two CPUs. In our Media Benchmarks, the Phenom 9500 scored 793, while the Core 2 Quad 6600 scored 1,036. The Q6600 is also faster in games and specialist applications such as 3D rendering and Folding@home. The G0 stepping Q6600 is renowned for being a great overclocker, as it's capable of running at 3.6GHz with a standard HSF, and more than 4GHz with more exotic cooling. In contrast, the Phenom 9500 wouldn't run any faster than 2.53GHz. However, the more expensive Q6700 isn't worth buying - it's nearly double the price of the Q6600, but only 7 per cent faster.

When the Q6600 debuted at £575 a year ago, we didn't reckon that it was worth splashing out the extra cash over a higher frequency dual-core CPU. However, as Intel has slashed the price of the Q6600, and more applications have been rewritten to take advantage of quad-core CPUs, the Q6600 has evolved into one of the best CPUs that money can buy. The only reason not to rush out and buy one immediately is Intel's range of 45nm Penryn architecture Core 2 Quads, which will be out early next year. These CPUs will be considerably faster, and more overclockable and energy-efficient than the Q6600.

• Multi-GPU graphics - 20th June 2008
• CPU water cooling - 17th June 2008
• Hard disks - 20th March 2008
• Audio hardware - 29th February 2008
• Graphics cards - 24th January 2008
• CPUs - 21st December 2007
• Motherboards - 13th November 2007

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