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29 September 1997 – Subject To Change
Thermal Management
10–1
10
Thermal Management
This chapter describes the 21164PC thermal management and thermal design consid-
erations.
10.1 Operating Temperature
The 21164PC is specified to operate when the temperature at the center of the heat
sink (T
c
) is 71.8°C for 400 MHz, 69.8°C for 466 MHz, or 67.5°C for 533 MHz.
Temperature (T
c
) should be measured at the center of the heat sink (between the two
package studs). The GRAFOIL pad is the interface material between the package
and the heat sink.
Table 10–1 lists the values for the center of heat-sink-to-ambient (
Θ
c
a) for the 413-
pin grid array. Table 10–2 shows the allowable T
a
(without exceeding T
c
) at various
airflows.
Note:
DIGITAL recommends using the heat sink because it greatly improves
the ambient temperature requirement.
1
With the heat-sink fan, performance does not depend on system airflow.
Table 10–1
Θ
c
a
at Various Airflows
Frequency: 400 MHz, 466 MHz, and 533 MHz
Airflow (linear ft/min)
100
200
400
600
800
1000
Θ
c
a with heat sink 1 (°C/W)
3.2
1.7
0.95
0.75
0.65
0.55
Θ
c
a with heat sink 2 (°C/W)
(includes 52×10 mm fan)
0.75
1