Software Functional Overview
Before disabling power, platform designers should incorporate some time that allows the OS to run its critical shutdown operation. There is no requirement for a minimum shutdown operation window that commences immediately after the temperature reaches _CRT. This is because
−Heat might rise rapidly in some systems and slower on others, depending on casing design and environmental factors.
−Shutdown can take several minutes on a server and only a few short seconds on a
Because of this indistinct discrepancy and the fact that a critical heat situation is a remarkably rare occurrence, ACPI does not specify a target window for a safe shutdown. It is entirely up to the OEM to build in a safe buffer that it sees fit for the target platform.
3.5.17 Other Implementation Of Thermal Controllable Devices
The ACPI thermal event model is flexible enough to accommodate control of almost any system device capable of controlling heat. For example, if a mobile PC requires the battery charger to reduce the charging rate in order to reduce heat it can be seamlessly implemented as an ACPI cooling device. Associating the charger as an active cooling device and reporting to the OS target temperatures that will enable or disable the power resource to the device do this. Figure as following illustrates the implementation. Because the example does not create noise, this will be an implementation of silence mode.
90
_CRT
60
55
_AC0 Fan on/off
50
_PSV Throttle CPU
45
_AC1 Reduce charge
40rate
35
30
25
20
15
10
5
Figure 3-5 Other Thermal Control
3.5.18 Thermal Control Methods
Control methods and objects related to thermal management are listed in the table below.
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