Intel Core 2 Duo

Core 2 Duo is Intel's mainstream processor brand, and it finds its way into a wide range of devices, from gaming PCs to business laptops and even iMacs.

But it's a broad label. The range currently runs to no fewer than 14 desktop chips with three different cores and significantly different characteristics. There are also 18 laptop CPUs, which fall outside the scope of this month's Labs.

The first Core 2 Duo processors were the E6000 series, launched back in 2006, based on the 65nm Conroe core. These were arrestingly powerful CPUs for their time, and two of them - the 2.4GHz E6600 and the 2.66GHz E6700 - are still in production today. Their benchmark scores of 1.18 and 1.30 are still respectable too.

Last year, they were joined by the E6750 and E6850, based on the same core but using higher clock speeds and a faster front side bus (1,333MHz rather than the original 1,066MHz). They achieve better performance, yet currently sell at lower prices, leaving the older Core 2 Duos looking redundant.

The E6000 series also originally included some cheaper models - the E6300 and E6400 - with a reduced L2 cache (2MB instead of 4MB). These have since been replaced by the E6320 and E6420, with full 4MB caches, and are joined by an E6550 that supports a 1,333MHz front side bus. But thanks to relatively low clock speeds, these chips still don't match the performance of even their older brethren, and it's hard to recommend any of them when £100 will get you a far more capable E6750.

The Conroe-based Core 2 Duos were followed last year by the E4000 series, based on the more recent Allendale core. This range is inferior to the E6000 series in several ways: clock speeds only go up to 2.4GHz, the front side bus runs at just 800MHz and, as with the original low-end Core 2 Duo CPUs, they only have 2MB of L2 cache. This does make E4000s significantly cheaper than the E6000s: the E4500 costs just £64 but achieves benchmark results not far off the £91 E6320.

But, as our graph on p88 illustrates, neither range is particularly impressive. At the lower end of the performance scale, our benchmarks showed the lesser E4000 chips to be little better than Intel's far cheaper Pentium Dual-Core processors. And while the higher-end E6000s aren't lacking in power, an AMD Athlon will give you comparable performance for less money - albeit with almost twice the thermal design power (125W as opposed to the Core 2 Duo's 65W).

Thankfully, the Core 2 Duo range has a trump card: the new E8000 series, launched in January and based on the new 45nm Wolfdale core. The design expands on the original E6000 with 6MB L2 caches, 1,333MHz front side buses across the board and clock rates up to 3.16GHz - the sort of speed normally reserved for the Core 2 Extreme range. TDP remains at 65W.

The benchmark results speak for themselves: even the low-end model scored a roaring 1.42, and the most powerful achieved a stratospheric 1.63. And the best part is the price: the E8200 can be had for just £96. It's clear that Intel's move to 45nm technology is paying off, as in terms of both raw power and bang per buck the E8000 wipes the floor with the E6000 series.

So as a whole, the Core 2 Duo range is a mixed bag. At the lower end, the E4000s deliver uninspiring performance for an unattractive price; it's hard to see why you'd choose one over a Pentium Dual-Core.

The mid-range E6000s are distinctly more capable, but the relative pricing of the various models makes no sense. The best buy is the E6750, which gets you similar performance to an AMD Athlon 6400+ in a more energy-efficient chip, although the Athlon is slightly cheaper.