We have recently seen a tremendous increase in the need for effective CPU cooling. The simple heatsink plus cheap fan combination favored by your local PC superstore just cannot cut the mustard when dealing with CPUs dissipating 70 W and upwards. Our previous tests have shown that the future definitely belongs to the composite coolers (aluminum in combination with copper) and the all-copper coolers. The simpler alternatives are just unable to cope with the amount of heat generated by today's CPUs.

Manufacturers of premium coolers have taken their lead from the aerospace industries, using special heat sink profiles and fan impellor geometries designed to optimize airflow. However, the familiar conflict of interest between cooling effectiveness and noise levels remains very much in evidence. The best solution available right now comes from Zalman, with its skived fin design CNPS7000CU air cooler. This large cooler costs in the range of $45-55 and is ideal for overclocking.

If you want more cooling power than this, you have to look at water-cooling. The Hydrocool 200 from Corsair is unbeatable in this department at the moment. The THG lab has been putting this device through its paces for several weeks now, and we'll have a review here for you very soon. At over $200 it's not exactly cheap, but it outperforms the established competition from the likes of Innovatek. This is not surprising; the design was provided by Delphi, the automotive aircon systems manufacturer. It lets you overclock even premium CPUs like the 3 GHz P4 by over 20 percent.

Even better cooling performance is available from "evaporator" systems. These use a special cooling medium that is forced through a cycle of evaporation, from liquid to gas, and condensation back again, from gas to liquid.

This market segment is populated by somewhat unfamiliar companies - apart from Asetek and Chip-Con, there are no other well-known manufacturers represented. Products from Asetek (VapoChill Puts a Pentium 4 with 800 MHz FSB within Reach ) and Chip-Con (The Iceman Cometh: P4 at 4.1 GHz ) have passed through the THG lab.