Hardware Reference
In-Depth Information
boutique models costing even more. You'll invariably pay more for the most efficient,
best-cooling active heatsinks, and those overclockers who swear by these devices usually
also believe that the extra expense is worthwhile.
Note
Passive
heatsinks are basically aluminum-finned radiators that are more difficult to integrate
because they rely on airflow from an external source, usually provided by a chassis-mounted
fan that sometimes features a duct to direct airflow directly through the fins on the heatsink.
Passive heatsinks are seldom used on current processors, although they have been popular in
the past on name-brand systems. Passive heatsinks connected to heatpipes are currently pop-
ular for chipset cooling.
“Boutique” Heatsinks
A large market exists for high-end “boutique” heatsink products, many of which have
shapes and designs that would qualify them more as industrial art than an internal com-
puter component. These fancy heatsinks are popular with overclockers as well as those
who like to modify their systems in general.
Although I certainly appreciate a good-looking piece of hardware as much as anybody,
as an engineer I am more concerned about performance than appearance. Most of the
boutique designs do in fact have outstanding thermal performance, but the actual level
of performance is rarely documented (making comparisons difficult) and may come with
other costs besides a high price. These drawbacks include awkward sizes, excessive
weightthatcoulddamagetheprocessorormotherboard,andattachmenthardwarethatcan
be difficult to use.
Perhaps my main beef is the lack of technical documentation. The primary specification
for the thermal performance of a heatsink is the thermal resistance, specified in degrees
Celsius per watt. The lower this figure, the better the performance. Unfortunately, most
of the boutique heatsinks on the market don't include this figure in their specifications.
Without knowing the thermal resistance, you have no easy way to compare the perform-
ance of one heatsink to another.
Heatsink Ratings and Calculations
When cooling a processor, the heatsink transfers heat from the processor to the air. This
capability is expressed in a figure known as
thermal resistance
, which is measured in de-
grees Celsius per watt (C/W). The lower the figure, the lower the thermal resistance and
the more heat the heatsink can remove from the CPU.
To calculate the heatsink your processor requires, you can use the following formula:
