Intel QX68000 Core 2 Extreme, Design Manual

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Thermal Metrology
Thermal and Mechanical Design Guidelines 25
3.1.1 Example
The cooling performance, Ψ
CA,
is then defined using the principle of thermal
characterization parameter described above:
• The case temperature T
C-MAX
and thermal design power TDP given in the processor
datasheet.
• Define a target local ambient temperature at the processor, T
A
.
Since the processor thermal profile applies to all processor frequencies, it is important
to identify the worst case (lowest Ψ
CA
) for a targeted chassis characterized by T
A
to
establish a design strategy.
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 specific Intel processor thermal specifications, and are for
illustrative purposes only.
Assume the TDP, as listed in the datasheet, is 100W and the maximum case
temperature from the thermal profile for 100W is 67 °C. Assume as well that the
system airflow has been designed such that the local ambient temperature is 38°C.
Then the following could be calculated using equation 1 from above:
Ψ
CA
= (T
C,
– T
A
) / TDP = (67 – 38) / 100 = 0.29 °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
≤ 0.10 °C/W, solving for equation 2 from above, the performance of
the heatsink would be:
Ψ
SA
=
Ψ
CA
− Ψ
CS
= 0.29
−
0.10 = 0.19 °C/W