Intel has released its first ever quad-core processor, the Core 2 Extreme QX6700.

Although announced today, this processor won't actually be available to buy until 14 November 2006. Retail pricing hasn't been confirmed, but it should end up at the same price as the 2.93GHz Core 2 Duo Extreme Edition X6800, which sells for £700.

Previously codenamed Kentsfield, the QX6700 remains in Socket 775 form factor and, with a quick Bios update, can be used with the majority of Core 2 Duo compatible motherboards.

Clocked at 2.66GHz, the same as a Core 2 Duo E6700, the Core 2 Extreme QX6700 is actually two Core 2 Duos fitted together in a single package. As a result, the L2 cache is made up of two 4MB caches, totalling 8MB. As first stated in our news story, Intel will continue to make quad-core processors in this way beyond 2007.

Not being a native quad-core part, this CPU isn’t particularly energy efficient. It has a 130W envelope, which means it dissipates twice as many watts compared to a Core 2 Duo. 130W was typical of the high-end, hot and hungry Pentium D processor.

Users shouldn’t expect a doubling of performance with double the cores. Firstly, the Front Side Bus (FSB), which dictates how fast the CPU can transfer data to Ram and other devices, remains at 1,066MHz. This means the four cores must share and jostle for bandwidth to the Northbridge. Secondly, most day to day software isn’t yet optimized for quad core; a few programs get confused and will not even run when they see four cores.

In our PCmark05 CPU test the QX6700 thrashed out a score of 8,100; the highest score we've ever seen and nine per cent higher than the X6800’s 7,404. In 3Dmark06 CPU test the QX6700 blew everything else away with a score of 3,961, beating the previous top dog, the x6800, by 58 per cent.

Head to our benchmarking site to read the full performance scores of the QX6700.

These are impressive scores, but ultimately only a set of theoretical figures. Real-world tests proved far less thrilling. In our review of the Hi-Grade Ultis Tachyon quad-core PC (review coming later today), the QX6700 processor returned a score of 345 in Sysmark 2004 SE, which is about the same as a Core 2 Duo E6700 would score.

Real benefits are seen in video and audio encoding. In Cinebench 2003, a benchmark that tests rendering capabilities, the QX6700 scored a massive 1,442 points – 55 per cent higher than the Core 2 Extreme X6800. High-definition video editing and compression will get the biggest boost from two extra cores.

In terms of gaming, we couldn't get Far Cry to run and have also heard reports of Call of Duty 2 causing similar problems. Like all other software, new code will have to be written to take advantage of four cores and some games may need new patches to allow compatibility.

Continue to page 2 to read about the motherboard and overclocking...