Thermal/Mechanical Reference Design
32 Dual-Core Intel® Xeon® Processor 5100 Series Thermal/Mechanical Design Guide
Figure 2-13 illustrates the combination of the different thermal characterization
parameters.
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 EMTS.
• 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:
Figure 2-13. Processor Thermal Characterization Parameter Relationships
HEATSINK
IHS
TIM
PROCESSOR
T
S
T
C
SOCKET
SA
CS
CA
HEATSINK
IHS
TIM
PROCESSOR
T
S
T
CASE
T
LA
SOCKET
SA
CS
CA
HEATSINK
IHS
TIM
PROCESSOR
T
S
T
C
SOCKET
SA
CS
CA
HEATSINK
IHS
TIM
PROCESSOR
T
S
T
CASE
T
LA
T
LA
SOCKET
SA
CS
CA
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