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6.
Alternative Cooling Solutions
In addition to passive heatsinks, fan heatsinks and system fans, other solutions exist for cooling
integrated circuit devices. For example, ducted blowers, heat pipes and liquid cooling are all capable of
dissipating additional heat. Due to their varying attributes, each of these solutions may be appropriate for
a particular system implementation. More information on this topic can be located on Intel's web site at
http://developer.intel.com/.
6.1.
Ducting
Ducts can be designed to isolate the processor from the effects of system heating (such as add-in cards),
and to maximize the processor cooling temperature budget. Typical temperature rise from external
ambient to the local-ambient near the processor can be greater than 10°C. Air provided by a fan or
blower can be channeled to the processor and heatsink with little or no rise from the external ambient
temperature.
6.1.1.
Ducting Placement
When ducting is to be used, it should direct the airflow evenly from the fan through the length of the
heatsink. This should be accomplished, if possible, with smooth, gradual turns, as this will reduce air
impedance. Sharp turns in ducting should be avoided as they increase friction and drag and will greatly
reduce the volume of air reaching the processor heatsink.
6.2.
System Components
6.2.1.
Placement
Peripherals such as CD-ROMs, floppy drives, and hard drives can be placed to take advantage of the
fan's movement of ambient air (i.e., near intake or exhaust fans or venting). Some add-in cards often
have a low tolerance for temperature rise. These components should be placed near additional vents if
they are downstream of the processor to minimize temperature rise.
6.2.2.
Power
Some types of drives, such as a floppy drive, do not dissipate much heat, while others (read/write CD-
ROMs, hard drives) dissipate a great deal of heat. These hotter components should be placed near fans
or vents whenever possible. The same can be said for some types of add-in cards. Some PCI cards are
very low wattage (5W) while others can be as high as 25 watts, per PCI specification. Great care should
be taken to ensure that these cards have sufficient cooling.
249660-001
®
®
Intel
Pentium
III Processor in the FC-PGA2 Package Thermal Design Guidelines
21
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