Computer CPU Coolers ¶ 

Modern CPUs consume a lot of power as much as 130W. That power ends up as waste heat. In effect, a modern system has the equivalent of a 50W to 130W incandescent lightbulb burning constantly inside the case. That analogy understates the problem a lightbulb dissipates its heat from the relatively large surface of the bulb. A processor must dissipate the same amount of heat over the much smaller surface area of the processor die, typically about 0.25 square inch. Without an effective heatsink to draw away this heat, the processor might literally burn itself to a crisp almost instantly.

Nearly all systems deal with this heat problem by placing a massive metal heatsink in close contact with the processor die (or integrated heat spreader) and using a small fan to draw or push air through the heat-sink fins. This device is called a heat-sink/fan (HSF) or CPU cooler. As the power consumption of processors has continued growing, so too has the size and mass of the heatsinks they use. Even the stock coolers packaged with retail-boxed processors nowadays are often quite large and heavy. For example, Figure 5-6 shows a stock Intel Pentium 4 CPU cooler on the left and a Thermalright XP-120 aftermarket CPU cooler on the right, with a pair of AA batteries shown for scale.

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Figure 5-6: Intel stock CPU cooler (left) and Thermalright XP-120 CPU cooler, with AA batteries shown for scale

Heatsinks are constructed with different materials, according to their prices and intended uses. An inexpensive heatsink, or one intended for use with a slower processor, is likely to be of all-aluminum construction. Aluminum is inexpensive and relatively efficient in transferring heat. Copper is much more expensive than aluminum, but is also much more efficient in transferring heat. Accordingly, a more expensive heatsink, or one intended for a faster processor, might be constructed primarily of aluminum, but with copper surfaces where the processor contacts the heatsink. The most expensive heatsinks, and those intended for use with the fastest processors, are constructed of pure copper.

Heatsink/fan units also differ in the type and size of fan they use, and how fast that fan runs. Fan speed is an issue, because all other things being equal, a faster-running fan produces more noise. For equal air flow, a larger, slower fan produces less noise than a smaller, faster fan. Fan sizes have increased as processor speeds have increased, to provide the high air flow volume needed to cool the heatsink while keeping fan speed (and noise) at a reasonable level. For example, heatsinks for Pentium II processors used 30 mm fans. Heatsinks for early Pentium 4 and Athlon 64 processors typically used 60 mm or 70 mm fans. Some third-party "performance" heatsinks targeted at overclockers use 80 mm, 92 mm, or 120 mm fans. Some even use multiple fans.

In general, we recommend using the CPU coolers that are bundled with retail-boxed processors. The bundled coolers are generally midrange in terms of performance and noise level neither as efficient nor as quiet as good aftermarket coolers, but less costly.

However, if you are concerned about PC noise, a third-party CPU cooler is the way to go. You can spend anything from about $15 to more than $100 on a quiet CPU cooler, depending on the processor you're using and just how quiet and efficient you require the cooler to be. Arctic Cooling (http://www.arctic-cooling.com) makes several models in the $15 to $30 range that are reasonably quiet and efficient. If you're willing to spend a bit more, look at Zalman 7000- and 7700-series coolers (http://www.zalmanusa.com), which are in the $30 to $45 range, and are extremely quiet and so efficient that some models can be run fanless (and therefore completely silent) with some processors. Finally, if only the best will do and you're willing to pay $60 or more for a CPU cooler, choose a Thermalright (http://www.thermalright.com) model and add one of the fans recommended by Thermalright.

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