Intel X5365 Design Guide - Page 36

Example, Processor Thermal Characterization Parameter Relationships

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Thermal/Mechanical Reference Design Figure 2-15. Processor Thermal Characterization Parameter Relationships 2.3.2.1 Example The cooling performance, ΨCA, is then defined using the principle of thermal characterization parameter described above: • Define a target case temperature TCASE_MAX and corresponding TDP, given in the processor Datasheet. • Define a target local ambient temperature at the processor, TLA. 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 Datasheet TDP is 85 W and the case temperature specification is 68 °C. Assume as well that the system airflow has been designed such that the local processor ambient temperature is 45°C. Then the following could be calculated using equation (2-3) from above: Equation 2-5.ΨCA = (TCASE - TLA) / TDP = (68 - 45) / 85 = 0.27 °C/W To determine the required heatsink performance, a heatsink solution provider would need to determine ΨCS performance for the selected TIM and mechanical load configuration. If the heatsink solution was designed to work with a TIM material performing at ΨCS ≤ 0.05 °C/W, solving for equation (2-4) from above, the performance of the heatsink would be: Equation 2-6.ΨSA = ΨCA − ΨCS = 0.27 − 0.05 = 0.22 °C/W If the local processor ambient temperature is assumed to be 40°C, the same calculation can be carried out to determine the new case-to-ambient thermal resistance: Equation 2-7.ΨCA = (TCASE - TLA) / TDP = (68 - 40) / 85 = 0.33 °C/W It is evident from the above calculations that, a reduction in the local processor ambient temperature has a significant positive effect on the case-to-ambient thermal resistance requirement. 36 Quad-Core Intel® Xeon® Processor 5300 Series Thermal/Mechanical Design Guidelines (TMDG)

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Thermal/Mechanical Reference Design
36
Quad-Core Intel® Xeon® Processor 5300 Series Thermal/Mechanical Design Guidelines (TMDG)
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, given in the
processor Datasheet
.
•
Define a target local ambient temperature at the processor, T
LA
.
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 Datasheet TDP is 85 W and the case temperature specification is 68 °C.
Assume as well that the system airflow has been designed such that the local processor
ambient temperature is 45°C. Then the following could be calculated using equation
(2-3) from above:
Equation 2-5.
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 was designed to work with a TIM material
performing at
Ψ
CS
≤
0.05 °C/W, solving for equation (2-4) from above, the performance
of the heatsink would be:
Equation 2-6.
Ψ
SA
=
Ψ
CA
−
Ψ
CS
= 0.27
−
0.05 = 0.22 °C/W
If the local processor ambient temperature is assumed to be 40°C, the same
calculation can be carried out to determine the new case-to-ambient thermal
resistance:
Equation 2-7.
Ψ
CA
= (T
CASE
– T
LA
) / TDP = (68 – 40) / 85 = 0.33 °C/W
It is evident from the above calculations that, a reduction in the local processor
ambient temperature has a significant positive effect on the case-to-ambient thermal
resistance requirement.
Figure 2-15. Processor Thermal Characterization Parameter Relationships