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Hot computer? Try giving it a shower ...

You can't turn a hose-pipe on a PC chip when it gets over-heated. Or ... can you?

Printer technology may soon come to the rescue of over-clockers - computer speed freaks who risk over-heating their processor chips - if Hewlett-Packard can turn its latest research project into a commercial product.

It's a neat trick, using ink-jet technology to spray liquid coolant directly onto whichever part of the processor chip is over-heating.

The project is due for announcement after more feasibility studies, say managers at H-P labs in Bristol; but so far, there's good evidence that it will be useful - and more effective than other accelerated cooling devices, such as Peltier refrigeration packs clamped to the silicon surface.

Normally, of course, the point of an ink-jet printer is to spray liquid on paper, and hope that the liquid evaporates quickly, leaving a black mark behind (or a blue one, if it's blue ink).

The ink-jet chip cooler, however, has to be invisible; the liquid has to be pretty nearly pure, to avoid the build-up of residue. Apparently, this is the trick HP's researchers have pulled off.

The precision of an ink-jet print head is astonishing; and usually, this is used only to create a dot in the exact spot on the paper where it will look best. But in a chip cooler, it will enable the coolant to be directed at the exact cluster of transistors which are over-working.

When one of today's large computer processors is in operation, different parts of the circuit switch on and off to perform different types of task. Highly intensive processing, especially in some of the new graphics processors, can lead to intense localised over-heating.

Normal heat reduction involves clamping a simple metal heat sink to the surface of the chip. Air currents flowing over the metal cool it down, and it in turn prevents the silicon surface from getting too warm.

This can't prevent the temperature reaching quite alarming heights, especially when intensive processor operations are performed. So to make the heat sink more efficient, designers of large chips have resorted to special fans, attached to the heat-sink, to increase the air flow which keeps them cooler. Even so, it's not a good idea to touch a working chip - it will burn the fingers.

Over-clocking enthusiasts have resorted to expensive extra refrigeration units to overcome the problem. Some have actually filled the base of their personal computers with oil; others have used mechanical pumps. All these devices actually add, significantly, to the total amount of heat produced by the system; and can only cool down the average surface area of the silicon chip.

Only the HP coolant spray carries the promise of keeping the surface of the silicon uniformly cool.

The reason this is important is that silicon chips are, effectively glass. Heating one part of a bit of glass more than another part is a great way to crack it, as the hotter part expands faster than the cooler bits.

And of course, the faster you run the computer clock, the hotter the processor gets. Eventually, over-clocking causes errors to creep in and can even destroy the chip completely.

Meanwhile, here's a talking rabbit, and the end of the world: