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For the past few weeks, I've been moaning to anyone within earshot that computers these days aren't so much computers as fan heaters. I've been using a bare test rig set up in our labs - a system mounted on a specialised open test platform - testing PCI Express components and the like on an Intel 925X motherboard with a model 560 processor. And you can feel the heat being radiated when you sit near it.

But heat isn't the only thing: fear tends to make itself felt too. The new Intel-designed heatsink and fan combination is a brute of a thing, bristling with bifurcated aluminium fins and topped off with an amazingly powerful fan. Now usually you can stop a fan with your finger, but I wouldn't dare go near one of those things with a precious digit. There isn't even a plastic guard around the blades; mere safety features got in the way of airflow and so had to go. The design truly smacks of desperate measures taken to get within specification parameters and properly cool the CPU. But the result is that I won't have a new Intel-based system in my house, because they're ridiculously, stupidly hot.

Every electronic component has a datasheet, describing its physical, electrical and electronic operation. In the case of a lowly resistor it might be confined to a single side of A4; in the case of the datasheet entitled Intel Pentium 4 Processors 560, 550, 540, 520 and 520D, it's a 92-page technical heavyweight. Enter 'processor 560 datasheet' into www.intel.com's

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search field for the link.

The great thing about datasheets is that they're devoid of spin, sly phrasing or slippery definitions. They have to be accurate because they're the documents used by engineers designing systems. With this in mind, scroll to p74 and the table entitled 'Processor Thermal Specifications'. This lists, among other things, the TDP (thermal design power), which is the maximum power that the cooling system attached to the processor must be able to dissipate. Prepare yourself for a shock as you realise that heatsinks for model 550 and 560 processors must be designed to dissipate 115W.

Now pop over to www.argos.co.uk and type 'fan heater' into the search field. Most of the resulting appliances are rated at a maximum power of 2kW, but a few are as low as 500W. Take out your calculator, do a simple sum, and you'll see that five Intel Model 560 processors at full pelt actually are the equivalent of an electric heater.

To be fair to Intel, p74 of that datasheet also states: 'Analysis indicates that real applications are unlikely to cause the processor to consume maximum power dissipation for sustained periods of time'. This is largely true, although all you need to do is fire up SETI@home and use your motherboard's monitoring utility, then watch your processor's temperature rocket, to see that it's not always the case.

But there's a second problem: along with the latest 90nm fabrication process comes increased transistor leakage current. In simple terms this means that even when the processor is sitting idle, it's wasting power because its transistors are never fully switched off. It's the electronic equivalent of a tap in need of a new washer.

Ironically, the robust design of modern operating systems is also contributing to the problem. In the old days you could tell your system was heavily loaded - and therefore consuming maximum power - because it would regularly grind to a halt and you'd sit staring at the hourglass until it had finished chewing over a time-consuming operation.