In June 2003 Intel released the 3.2GHz Northwood Pentium 4 and after that it entered a black period with the Prescott core which failed miserably to produce decent clock speeds despite a move to a 90nm fabrication process.

To add to Intel's woes, Prescott consumed huge amounts of power and therefore shed enormous amounts of heat. In short, Prescott wasn't a good processor so Intel took the bold step of scrapping the NetBurst architecture, including Prescott's 65nm Tejas successor, and instead returned to the drawing board.

This gave AMD two years of grace, in which time its Athlon 64 and Opteron processors have ruled the roost. But now Intel is back and it means business. The new desktop processor that launches this month is Core 2 Duo. This is the second version of Intel's notebook Core processor, while the 'Duo' means it is dual core, so in time we shall doubtless see Core 3 Trio and then Core 4 Quadro, or perhaps that should be Core 4 Quattro.

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Core 2 Duo takes Intel's desktop processors in a new direction by putting the emphasis on efficiency rather than clock speed, so the new processors run on a Quad-pumped 266MHz Front Side Bus which is the equivalent of 1,066MHz.

However, the actual clock speeds are relatively low. The E6300 runs at 1.86GHz and costs £153, the E6400 is 2.13GHz and costs £182, the E6600 gives you 2.40GHz for £253 and the top-of-the-line E6700 has a clock speed of 2.67GHz and is on sale at £411.

In truth there's one more member of the family as the X6800 will be released about a month after the E series processors, but as this 2.93GHz Extreme processor will cost about £800 it's safe to say that sales will be low, even if its clock multiplier is unlocked and thus offers the prospect of some serious overclocking.

Intel Core 2 Duo has a much shorter pipeline length than the NetBurst Pentium 4 processors and it also uses the L2 cache as a shared pool, instead of dividing it into two even chunks with half reserved for each core. E6300 and E6400 have 2MB of L2 while the faster processors have 4MB of cache.

We can waffle on all day about the technical features but what counts is how the new processor performs. Recently this reviewer ran a group test of AM2 motherboards and in each case the AMD Athlon 64 FX-62 processor encoded a 350MB DivX movie file to DVD format in about 13 minutes. This test almost ignores the motherboard, chipset, memory and hard drive and puts the emphasis on the processor. The fastest AM2 board managed it in 13 minutes dead while the slowest came in at 13 minutes 22 seconds. In the bad old days before dual core processors, an Athlon 64 3800+ would take about half an hour.

By contrast the Core 2 Duo E6700 took 9 minutes 52 seconds and it is worth noting that the E6700 runs at 2.67GHz while the FX-62 has a clock speed of 2.8GHz, so the Core 2 Duo is much more powerful even at a nominally slower clock speed. And throughout the test the processor heatsink remained cool to the touch.

We also ran PCMark05 and the Core 2 Duo scored very well in every section of the benchmark, so make no mistake about it: Core2 Duo is a fabulous processor. But of course you need more than a bare chip inside your PC and this is where things get a bit confusing.

Intel supports Core 2 Duo with the current i975X chipset which it launched in December 2005 and, as Core 2 Duo uses the same LGA775 socket as the later models of Pentium 4, you might hope that this provides a direct upgrade path.

Think again.

Intel's Press kit includes a new revision of its D975XBX motherboard, however our year-old version of the same board wouldn't boot with Core 2 Duo installed even though we had upgraded the BIOS to the latest version. We understand that the new D975XBX board has significant revisions to the power regulation hardware, so if you want a Core 2 Duo you'll need a new motherboard in which case you may as well opt for the latest 965P chipset which launches alongside Core 2 Duo.

This chipset supports the fastest DDR2 memory and 1,066MHz FSB and is paired with the new ICH8 Southbridge which supports six SATA ports and HD audio. Unfortunately it doesn't support IDE, so most motherboards will have an add-in controller to allow you to connect your optical drive.

The ominous thing is that you can't connect a pair of Nvidia graphics cards in SLI on an Intel chipset motherboard as the graphics drivers require a suitable Nvidia chipset, so for the moment you are limited to a single graphics card or a pair of ATi cards in CrossFire. Gamers will, therefore, probably want to avoid the Intel chipsets.

Happily, Nvidia is a launch partner with the new Intel processor and it will unveil versions of the Nforce 500 chipsets that we saw with the AMD AM2 platform, and very good they are too. We'll reserve judgement until we've seen the new silicon but the Intel versions of Nforce4 ran incredibly hot which was probably related to the additional memory controller that Nvidia had to integrate in the Northbridge. AMD, of course, includes the memory controller in the CPU core while an Intel processor leaves the job to the chipset.

Nforce 500 is superb on the AMD platform and provided Nvidia's done the job correctly we expect that gamers will migrate to the Nforce 590 SLI in their droves. Still, gamers are only part of the market, so what about the rest of us?

We tested our E6700 on an Asus P5B Deluxe with P965 and ICH8R chipset, 2GB of Corsair XMS 8500 memory and a WD Raptor 150GB hard drive. The motherboard employs passive cooling throughout and during our performance testing we ran a noisy Sapphire X1900 XTX graphics card to generate some impressive results.

Once we were done we swapped the Sapphire for a passively cooled Asus EN7600GS graphics card and plugged in a fan controller on the CPU heatsink. We turned the controller down to barely audible levels and measured the heatsink temperature at 35 degrees while the graphics card touched 51 degrees during testing. Performance was adequate for all but the most demanding gaming and the noise level of the PC was very close to silent.

Gamers will love the new Core 2 Duo processor but we feel that it also has a place in the 'normal' home, as it is the ideal basis for a fast, quiet and cool PC. By contrast Athlon 64 suddenly looks a bit limp, so we expect that AMD will announce hefty price cuts soon, making this a win-win situation for the buying public.