Intel
®
Pentium
®
III Processor in the FC-PGA2 Package Thermal Design Guidelines
R
249660-001
25
7.3.
Local-ambient Temperature Measurement Guidelines
Local-ambient temperature, T
LA
, is the temperature of the ambient air surrounding the processor. In a
system environment, ambient temperature is the temperature of the air upstream of the processor and in
its close vicinity; or in an active cooling system; it is the inlet air to the active cooling device.
It is worthwhile to determine the local-ambient temperature in the chassis around the processor to better
understand the effect it may have on the case temperature.
The following guidelines are meant to alleviate the non-uniform measurements found in typical systems.
The local-ambient temperature is best measured as an average of the localized air surrounding the
processor. The following guidelines are meant to enable accurate determination of the localized air
temperature around the processor during system thermal testing. These guidelines are meant as a
reasonable expectation to ensure the product specifications are met.
7.3.1.
Local-ambient Temperature Measurement for a Passive
Heatsink
•
During system thermal testing, a minimum of two thermocouples should be placed approximately
0.5 to 1.0 inches (12.7 to 25.4 mm) away from the leading edge of the heatsink fins as shown in
Figure 7-2. The two thermocouples should be placed 2.0 (50.8 mm) inches apart (see top view in
Figure 7-2). This placement guideline is meant to minimize localized hot spots due to the
processor, heatsink, or other system components.
•
The thermocouples should be placed approximately 2 inches (50.8 mm) above the baseboard. This
placement guideline is meant to minimize localized hot spots from baseboard components.
•
T
LA
should be the average of the thermocouple measurements during system thermal testing.
Figure 7-2. Local-ambient Thermocouple Measurement Locations (Passive Heatsink)
Note:
Figure is not to scale. Locations are approximate and may vary depending on your system configuration.
