As the technologies evolve and the frequencies grow, the central processor generates more heat. That’s a well-known axiom. Working in its normal operational mode, a modern top-end processor dissipates about 100W of heat, thus calling for additional cooling, and this number only grows as you are trying to overclock the CPU.
For example, the peak heat dissipation of the Pentium 4 at 4GHz frequency and 1.8V Vcore is about 170W. No air cooler or even the most efficient water-cooling system can provide enough cooling for a processor with a heat dissipation of 170W. What’s more, overclockers don’t need just “enough cooling”, but want to reduce the temperature to the minimum. The maximum frequency the central or graphics processor can work at is not only limited by its technical specifics. The lower the temperature is, the higher the stability ceiling gets. This tendency is strong at any temperatures, so no cooling can be considered absolutely sufficient. Even if we compare the effect of -40°C with that of -80°C, we will see some frequency gain. This fact encourages overclocker enthusiasts to invent new cooling methods for their computer systems.
For today, we have a choice of several methods of the kind (in the order of increasing efficiency):
- Air cooling;
- Water cooling;
- Air or water cooling with Peltier-effect units (this combination helps to achieve temperatures below room temperature, but has low efficiency; we will discuss it later);
- Peltier or phase-change water-chillers (average temperatures range from +10°C to ‑30°C);
- Phase-change systems (from -5°C to -60°C);
- Dry ice plus ethanol (CO2 in the solid state, -78°C);
- Cascading phase-change systems (from -60°C to -100°C);
- Liquid nitrogen (-196°C).
But what is available for use as off-the-shelf products? Not much, actually: traditional air coolers and water-cooling systems, Peltier units and phase-change systems. Dry ice and liquid nitrogen don’t suit us since you can’t use them constantly (it is passive cooling, with the coolant evaporating). Cascade systems are very efficient, but bulky and difficult to manufacture. I doubt they will be produced in mass quantities for the use in computers in the near future. Water-chiller models are practically unavailable in the market and the efficiency of such an apparatus is questionable. So the most potent CPU cooling solution for today is the phase-change system.
The market of advanced cooling system is split between two companies from Denmark: Asetek (selling its products under the VapoChill trademark) and nVENTIV (earlier known as Chip-Con, the Prometeia trademark). Kryotech, the third player and the company who was the pioneer in the field, has left this market already. There are four systems available today. Asetek offers SE, PE and XE models, while nVENTIV promotes its cooling monster, the Mach II. This review is dedicated to the apex of Asetek’s model range, the VapoChill XE (eXtreme Edition) system, particularly with its version for Socket 478 processors.