Software Functional Overview
Active, Passive, and Critical Policies
There are three primary cooling policies that the OS uses to control the thermal state of the hardware. The policies are Active, Passive and Critical:
−Passive cooling: The OS reduces the power consumption of the system to reduce the thermal output of the machine by slowing the processor clock. The _PSV control method is used to declare the temperature to start passive cooling.
−Active cooling: The OS takes a direct action such as turning on a fan. The _ACx control methods declare the temperatures to start different active cooling levels.
−Critical trip point: This is the threshold temperature at which the OS performs an orderly, but critical, shut down of the system. The _CRT object declares the critical temperature at which the OS must perform a critical shutdown.
When a thermal zone appears, the OS runs control methods to retrieve the three temperature points at which it executes the cooling policy. When the OS receives a thermal SCI it will run the _TMP control method, which returns the current temperature of the thermal zone. The OS checks the current temperature against the thermal event temperatures. If _TMP is greater than or equal to _ACx then the OS will turn on the associated active cooling device(s). If _TMP is greater than or equal to _PSV then the OS will perform CPU throttling. Finally if _TMP is greater than or equal to _CRT then the OS will shutdown the system.
An optimally designed system that uses several SCI events can notify the OS of thermal increase or decrease by raising an interrupt every several degrees. This enables the OS to anticipate _ACx, PSV, or _CRT events and incorporate heuristics to better manage the systems temperature.The operating system can request that the hardware change the priority of active cooling vs passive cooling.
Dynamically Changing Cooling Temperatures
An OEM can reset _ACx and _PSV and notify the OS to reevaluate the control methods to retrieve the new temperature settings. The following three causes are the primary uses for this thermal notification:
−When a user changes from one cooling mode to the other.
−When a swappable bay device is inserted or removed. A swappable bay is a slot that can accommodate several different devices that have identical form factors, such as a
−When the temperature reaches an _ACx or the _PSV policy settings
In each situation, the
Resetting Cooling Temperatures from the User Interface
When the user employs the UI to change from one cooling mode to the other, the following occurs:
FIC A360 Service Manual |
