Intel Phi 7120A SC7120A Data Sheet
Product codes
SC7120A
Intel
®
Xeon Phi™ Coprocessor Datasheet
Document ID Number: 328209 003EN
34
For the region A-B, the cooling solution must maintain the case temperature below
95
95
°
C which will in turn maintain the coprocessor silicon junction temperature below
104
°
C. Assuming an air-cooled heat sink, at a maximum coprocessor power dissipation
of 198W (
) and an inlet air temperature of 45
°
C, the following equation
between coprocessor junction-to-case and case-to-air heat sink rating can be used to
determine the minimum necessary performance of a cooling system:
determine the minimum necessary performance of a cooling system:
T
junction
=
jc
* CPU
power
+
ca_req
* CPU
power
+ T
ambient
The heat sink must have a
ca_req
value adequate to keep the coprocessor junction
temperature at or below 104
°
C. The value for
jc
is a characteristic of the Intel
®
Xeon
Phi™ coprocessor and may be treated as 0.047, a constant.
As the coprocessor power level goes down (region B-C), it is desirable to keep the
junction temperature at or below a target temperature, here shown at 82
junction temperature at or below a target temperature, here shown at 82
°
C. Since each
coprocessor is programmed at the factory with the actual control temperature (T
control
),
a sophisticated cooling system may continuously read the junction temperature from
the card SMC and compare it to the programmed T
the card SMC and compare it to the programmed T
control
to adjust airflow. The change
in airflow over an air cooled heat sink affects the
ca
value. It is common to reduce fan
speed when maximum airflow is not needed to save power, reduce noise, or both.
In the B-C region, even though T
junction
is at a constant value, T
case
actually goes up a
little bit at lower power consumption levels. This is because a variable fan speed results
in a variable
in a variable
ca
, but a fixed
jc
.
Finally, in the C-D region where the coprocessor consumes very little power, an air
cooled heat sink using a variable fan speed to maintain a target junction temperature
may slow the airflow down too much. If the airflow is too low, the junction temperature
may be maintained properly, but the exhaust air temperature approaches the junction
temperature. Data center design considerations, including safety, may dictate that a
maximum allowable exhaust air temperature, such as 70
cooled heat sink using a variable fan speed to maintain a target junction temperature
may slow the airflow down too much. If the airflow is too low, the junction temperature
may be maintained properly, but the exhaust air temperature approaches the junction
temperature. Data center design considerations, including safety, may dictate that a
maximum allowable exhaust air temperature, such as 70
°
C, which in turn will set a
maximum limit on
ca
.
Figure 3-17 SE10X/7120X SKU Coprocessor Case Temperature (T
case)
vs Power
45.0
55.0
65.0
75.0
85.0
95.0
105.0
0
50
100
150
200
Temperature (
o
C)
Intel® Xeon Phi™ Coprocessor Si Power (W)
T
case
D
C
A
B
<95°C