Power Manager and ACPI/APM
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4/8/2010
Power Manager is not related to the Advanced Configuration and Power Interface (ACPI) or Advanced Power Management (APM) power management mechanisms. The ACPI specification defines a linear set of OS power states ranging from high-power/high-function to low-power/low-function. Power Manager enables OEMs to define any number of OS power states and does not require that they be ordered in a linear fashion.
You are encouraged to define OS power states that are situational and control device power, based on its location or environment. For example, you might define OS power states so that certain devices are turned off if the unit is not in a cradle, or allow devices to run at a high power consumption level if the device is plugged in. Similarly, you could define different idle or suspend states based on the OS environment. You are responsible for customizing Power Manager to recognize when transitioning between these states is appropriate or necessary.
System power states are significantly different from the ACPI model. However, device power states are superficially similar to ACPI device power states, although there are some subtle differences. For example, the D3 power state is related to a given device's ability to act as a wake source when the OS as a whole is suspended.