6.5 Thermal Management
ACPI is responsible for allowing the operating system to play an important part in the
system's thermal management. This results in the operating system having the ability to
take control of the operating environment by implementing cooling decisions according
to the demands put on the CPU by the application.
The conga-X945/XA945 ACPI thermal solution offers three different cooling policies.
•
Passive Cooling
When the temperature in the thermal zone must be reduced, the operating system
can decrease the power consumption of the processor by throttling the processor
clock. One of the advantages of this cooling policy is that passive cooling devices (in
this case the processor) do not produce any noise. Use the “passive cooling trip
point” setup node in the BIOS setup program to determine the temperature threshold
that the operating system will use to start or stop the passive cooling procedure.
•
Active Cooling
During this cooling policy the operating system is turning the fan on/off. Although
active cooling devices consume power and produce noise, they also have the ability
to cool the thermal zone without having to reduce the overall system performance.
Use the “active cooling trip point” setup node in the BIOS setup program to determine
the temperature threshold that the operating system will use to start the active
cooling device. It is stopped again when the temperature goes below the threshold
(5°C hysteresis).
•
Critical Trip Point
If the temperature in the thermal zone reaches a critical point then the operating
system will perform a system shut down in an orderly fashion in order to ensure that
there is no damage done to the system as result of high temperatures. Use the
“critical trip point” setup node in the BIOS setup program to determine the
temperature threshold that the operating system will use to shut down the system.
Notes
The end user must determine the cooling preferences for the system by using the setup
nodes in the BIOS setup program to establish the appropriate trip points.
If passive cooling is activated and the processor temperature is above the trip point the
processor clock is throttled according to the formula below.
∆
P[%] = TC1(T
n
-T
n-1
) + TC2(T
n
-T
t
)
•
∆
P is the performance delta
•
T
t
is the target temperature = critical trip point.
•
The two coefficients TC1 and TC2 and the sampling period TSP are hardware
dependent constants. These constants are set to fixed values for the
Copyright © 2006 congatec AG
X945m13
39/102