Advanced Configuration and Power Interface Specification

Thermal Management
11.3.1.2 _FPS (Fan Performance States)
The optional _FPS object evaluates to a variable-length package containing a list of packages that
describe the fan device’s performance states. A temperature reading above an active cooling trip
point defined by an _ACx object in a thermal zone or above a native active cooling trip point of a
device within the thermal zone causes OSPM thermal control to engage the appropriate
corresponding fan performance state from the list of fan performance states described by the _FPS
object if the fan device is present in the corresponding _ALx device list or if an entry exists for the
fan and trip point in the active cooling relationship table (_ART).
OSPM assumes a linear relationship for the acoustic impact and power consumption values between
successive entries in the fan performance state list. Notice that the acoustic impact measurement unit
(Decibels) is inherently non-linear. As such, the platform should populate _FPS entries as necessary
to enable OSPM to achieve optimal results.
Arguments:
None
Return Value:
A variable-length Package containing a Revision ID and a list of Packages that describe the fan
device’s performance states as described in Table 11-284 below.
Return Value Information
Package {
Revision, // Integer - Current revision is: 0
FanPState[0],
// Package
….
FanPState[n]
// Package
}
Each FanPState sub-Package contains the elements described below:
Package ()
{
Control,
TripPoint,
Speed,
NoiseLevel,
Power
}
// Fan P-State
// Integer DWORD
// Integer DWORD
// Integer DWORD
// Integer DWORD
// Integer DWORD
Table 11-284 FPS FanPstate Package Details
Field Format Description
Control Integer
(DWORD)
Indicates the value to be used to set the fan speed to a specific level using the
_FSL object.
If the fan device supports fine-grained control as indicated by the _FIF object,
this value is a percentage (0-100) of maximum speed level.
If the fan device does not support fine-grained control, this field is an opaque
value that OSPM must simply use in its evaluation of the _FSL object to set the
level to this performance state.
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