Advanced Configuration and Power Interface Specification

Thermal Management
Return Value:
None
11.4.7 _HOT (Hot Temperature)
This optional object, when defined under a thermal zone, returns the critical temperature at which
OSPM may choose to transition the system into the S4 sleeping state. The platform vendor should
define _HOT to be far enough below _CRT so as to allow OSPM enough time to transition the
system into the S4 sleeping state. While dependent on the amount of installed memory, on typical
platforms OSPM implementations can transition the system into the S4 sleeping state in tens of
seconds. If this object it present under a device, the device’s driver evaluates this object to determine
the device’s hot cooling temperature trip point. This value may then be used by the device’s driver to
program an internal device temperature sensor trip point.
Arguments:
None
Return Value:
An Integer containing the critical temperature threshold in tenths of degrees Kelvin
The return value is an integer that represents the critical sleep threshold tenths of degrees Kelvin. For
example, 300.0K is represented by the integer 3000.
11.4.8 _MTL (Minimum Throttle Limit)
This object, when defined under a thermal zone, returns the minimum throttle limit of a zone. This
will determine how much a thermal zone limits the performance of its controlled devices. This value
can be used by OSPM to calculate the changes in performance limits it applies to the devices of the
thermal zone.
Arguments:
None
Return Value:
An Integer value with the current minimum throttle limit, expressed as a percentage
11.4.9 _NTT (Notification Temperature Threshold)
This optional object may be defined under devices containing native temperature sensors and
evaluates to the temperature change threshold for the device where the platform requires notification
of the change via evaluation of the _TPT object.
Arguments:
None
Return Value:
An Integer containing the temperature threshold in tenths of degrees Kelvin.
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