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All electronic circuits discharge heat generated by the movement of electrons. As operating frequencies increase, thermal loads go up (assuming die sizes and fabrication techniques remain constant). Given these facts, a successful overclocker must pay attention to cooling systems and sometimes devise external solutions dedicated to dissipating heat and regulating the processor's temperature.
Most common thermal regulation solutions are built around the concept of forced-air cooling. The standard processor cooler includes a massive metal heatsink and a high revolutions-per-minute (RPM) fan to dissipate heat through convection. Forced-air coolers represent the most cost-effective solution for the widest range of system platforms; the parts are simple in design and readily available. Many solutions are possible, but a heatsink cooler is still the best choice for most overclocking scenarios.
Size, density, shape, and material influence a heatsink's ability to dissipate heat. The best coolers available are often fabricated entirely of copper, with its excellent thermal transfer properties. Copper is also the most expensive option, due to high procurement and manufacturing costs. Aluminum is the most widely used heatsink material. It provides acceptable thermal conductivity at a relatively low cost. At the least expensive end of the heatsink spectrum is cast iron. Iron is a poor thermal conductor, and these coolers should be avoided.
Many of today's high-quality heatsink coolers combine two or more metals to maximize thermal conductivity while minimizing cost. The most cost-effective designs use copper as the core material (due to its superior thermal efficiency) and aluminum for the radiating fins (due to its stress-handling properties). This combination provides a good cooling system with improved ruggedness. Copper is not as rigid as aluminum, so you must exercise great care when handling and installing copper coolers.
Cooling fan efficiency is directly proportional to size, RPM, and blade design. The most common fans are 60 millimeters across, with average turning rates in the range of 4500 to 6000 RPM. Fans that operate at high speeds move more air for their size than those with low RPM, though high-speed fans also create more noise. For example, 60-millimeter high-speed fans exceeding 7000 RPM are available for midrange coolers, but prove too noisy for most users.
Large fans 70 to 90 millimeters in size usually move more air than small ones (assuming that the RPM is the same). An adapter mechanism is often required to take advantage of a large fan, however, since most heatsink designs are built around a 60-millimeter fan.
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