Intel Xeon Processor with 800 MHz System Bus Thermal/Mechanical Design Guide

22 Intel® Xeon™ Processor with 800 MHz System Bus Thermal/Mechanical Design Guidelines
Thermal/Mechanical Reference Design
2.3.2.1 Example
The cooling performance, Ψ
CA,
is then defined using the principle of thermal characterization
parameter described above:
• Define a target case temperature T
CASE-MAX
and corresponding TDP at a target frequency, F,
given in the Intel® Xeon™ Processor with 800 MHz System Bus at 2.80 GHz and 3.60 GHz
Datasheet.
• Define a target local ambient temperature at the processor, T
LA
.
Since the processor thermal specifications (T
CASE-MAX
and TDP) can vary with the processor
frequency, it may be important to identify the worse case (lowest Ψ
CA
) for a targeted chassis
(characterized by T
LA
) to establish a design strategy such that a given heatsink can cover a given
range of processor frequencies.
The following provides an illustration of how one might determine the appropriate performance
targets. The example power and temperature numbers used here are not related to any Intel
processor thermal specifications, and are for illustrative purposes only.
Assume the Intel® Xeon™ Processor with 800 MHz System Bus at 2.80 GHz and 3.60 GHz
Datasheet TDP is 85 W and the case temperature specification is 68 °C for a given frequency.
Assume as well that the system airflow has been designed such that the local processor ambient
temperature is 4 5°C. Then the following could be calculated using equation 1 from above for the
given frequency:
Equation 10. Ψ
CA
= (T
CASE
– T
LA
) / TDP = (68 – 45) / 85 = 0.27 °C/W
To determine the required heatsink performance, a heatsink solution provider would need to
determine Ψ
CS
performance for the selected TIM and mechanical load configuration. If the
heatsink solution were designed to work with a TIM material performing at Ψ
CS
≤ 0.05 °C/W,
solving for equation 2 from above, the performance of the heatsink would be:
Figure 2-6. Processor Thermal Characterization Parameter Relationships
HEAT S I NK
IHS
TIM
PROCESSOR
T
S
T
C
SOCK E T
Ψ
S
Ψ
C
HEAT S I NK
IHS
TIM
PROCESSOR
T
S
T
CASE
SOCK E T
Ψ
S
Ψ
C
HEAT S I NK
IHS
TIM
PROCESSOR
T
S
T
C
SOCK E T
Ψ
S
Ψ
C
HEAT S I NK
IHS
TIM
PROCESSOR
T
S
T
CASE
SOCK E T
Ψ
S
Ψ
C