Keeping Your Cool...

When overclocking, pushing our processors to faster speeds and higher performance, thermal management has become increasingly crucial. Maintaining the proper thermal environment is key to reliable, long-term system operation. The overall goal in providing the proper thermal environment is keeping the processor below its manufacturer specified maximum case temperature. Good quality heatsinks provide improved processor heat dissipation through increased surface area and concentrated airflow from attached fans. In addition, interface materials allow effective transfers of heat from the processor to the heatsink.

What is required in a good heat sink?

Think of the heatsink as simply a heat exchanger, exchanging the hotter temperature of the processor for the cooler temperature of its ambient environment. The heatsink's ability to perform this task can be measured using the so-called thermal resistance theta (in °C/W or degrees Celsius per watt of electricity). For example, a thermal resistance of 2°C per watt means that for each watt the processor uses, the temperature for will increase by two degrees Celsius. If a given processor uses 15w. and you're using a heat sink with a thermal resistance of 2 °C/W, the CPU temperature will raise by about 30°C. The lower the thermal resistance of a heat sink is, the better. Good Super7 CPU heatsink/fan combinations have a thermal resistance of about 1 to 1.5 °C/W. If you are thinking of overclocking you will want a cooler that has a thermal resistance capability of or below 1°C/W. The more the surface area of the heatsink, the better it cools. A larger surface can be attained by making the heat sink bigger, or by using finer fins (the extrusions of metal allowing air to pass through).  The ideal is of course a large heatsink with very fine fins. Good air circulation through the cooling fins must be given.  With poorly designed pin fin heat sinks this can be a problem. The bottom of the heatsink that will touch the processor needs to be perfectly flat to provide the proper thermal interface. A rough or uneven surface on this side of the cooler will leave gaps between the CPU and the heatsink reducing thermal conductivity. This can be ameliorated somewhat with the use of thermal grease or other heat conductive compounds but as a good rule of thumb, it is a good idea to pass on the purchase of any heatsink with an uneven bottom.
The primary material used to create today's heatsink is an aluminum allot but there are a few companies working on producing copper or aluminum-clad copper heatsinks. The best material would be silver but cost considerations make this a somewhat unrealistic material to use for mass production. Copper is almost twice as good as Aluminum in thermal conductivity and almost as good as Silver. So why aren't heatsinks made of copper available? Well although copper transfers heat efficiently it isn't as efficient as aluminum at radiating it to its ambient environment. This is addressable through the use of convection (using a fan to blow the heat off of the surface of the copper) but, it is also much easier, and therefore more cost efficient, to fabricate aluminum through casting, extrusion and machining than copper.

The Fan

Heat is transferred to its ambient environment much more rapidly through the use of convection (the air blowing across the fins of the heatsink) and if you are into overclocking a good fan or series of fans is a must. You will want to look for a heatsink fan that is a ball bearing fan at a minimum of 50mm in diameter. Sleeve bearing fans tend to fail much more often than ball bearing fans making a pretty awful grinding noise in the process. They also tend to vibrate more than ball bearing fans and therefore should be avoided. Something else to consider is the noise factor of the fan the faster the rotation speed of the fan the greater the sound output. You should only be able to hear the sound of the airflow and not the motor. A fan motor that's louder than the noise of the airflow usually is a low-quality fan. Don't buy fans that have a buzzing or whining sound. Most CPU heatsink fans operate at speeds from 4-6000rpm. Most fans are rated according to their ability to pesh air in cubic feet per minute (CFM). Typical CFM values are between 5 and 9 CFM, going up to as much as 20 CFM for high-end units.

EISCA Heatsinks

EISCA stands for "Enhanced Intelligent System Cooler Architecture". A new standard for "intelligent" cooling, the heart of EISCA is a totally new heatsink design; a thermal sensor is integrated into the heatsink, directly on the CPU interface. The advantage is that the temperature measurements are much more accurate than those of a thermal sensor located underneath the CPU (like the sensors found on boards like the ASUS TX97). An EISCA-compliant system can monitor four voltages (12V, 5V, 3.3V, and Vcore), the rpm of up to two fans, and two temperatures (CPU and motherboard/environment temperature). Many of the new Super7 mainboards support this standard I know that the FIC VA-503+ that I use does as do many others. If you are into overclocking you may want to include this feature in the next mainboard you choose.

VM-PCWARE   high performance heatsinks. They offer several Global Win models at good prices. Also in their product range:   hard drive coolers and case fans. International orders - VISA/MasterCard accepted.

Tom Mosher's SDS Mark II is a great site if you're looking to buy heatsinks. International orders - all major credit cards are accepted.

Newark Electronics Large selection of Thermalloy heatsinks:
$25.00 min. per order

The IERC p5 series heatsinks
John Corwith offers IERC p5 series heatsinks at reasonable prices, without minimum order.

Heatsink manufacturers that offer online ordering:

TennMax online ordering - buy CPU heatsinks & graphics card coolers directly from TennMax.

A&P Tech factory store - buy CPU heatsinks & graphics card coolers directly from A&P Tech.

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