Table of Contents
Advertisement
R
5.
Designing for Thermal Performance
5.1.
Airflow Management
It is important to manage the volume and velocity of air that flows within the system, as well as how it
flows, to maximize the amount of cool air that flows over the processor. Total system airflow can be
increased by adding one or more fans to the system, or by increasing the output (increasing the speed or
size) of an existing system fan(s). Managing the airflow direction using baffles or ducts can also increase
local airflow. An important consideration in airflow management is the temperature of the air flowing
over the processor. Heating effects from chipset, voltage regulators, add-in boards, memory, and disk
drives greatly reduce the cooling efficiency of this air, as does re-circulation of warm interior air through
the system fan. Care must be taken to minimize the heating effects of other system components, and to
eliminate warm air re-circulation.
If no air path exists across the processor heatsink, the warm air from the processor will not be removed
from the system, resulting in localized heating ("hot spots") around the processor(s). Passive heatsink fin
designs should be aligned with the direction of the airflow.
Figure 5-1 shows two examples of air exchange through a µATX style PC chassis. The system on the left
is an example of a center mounted power supply, and the one on the right is an example of a top mounted
power supply. Both are examples of good air exchange incorporating the power supply fan as well as an
additional system fan (additional system fan shown as the three large arrows entering the front bezel).
For further information, reference the system thermal design suggestions for the appropriate form factor
available at http://www.formfactors.org/.
Figure 5-1. Example of Air Exchange Through a µATX PC Chassis
249660-001
®
®
Intel
Pentium
III Processor in the FC-PGA2 Package Thermal Design Guidelines
System Fan Intake
System Fan Intake
15
Advertisement
Table of Contents
