Windows Power Management Architecture

Efficient power management requires tight integration between a computer’s BIOS or firmware, hardware, and software, including device drivers, Windows, and applications. The Windows Kernel Power Manager orchestrates power management in the following steps:

(1) When a computer starts, the Windows processor driver retrieves information about the computer’s support for the Advanced Configuration and Power Interface (ACPI) specification from the BIOS or firmware.

(2) The Windows processor driver provides information, such as which sleep and processing states the processor(s) support, to the Windows Kernel Power Manager.

(3) Hardware device drivers provide information about the power management support the device provides. Because the ACPI specification defines more system sleep states than device sleep states, device sleep states must be mapped to an available system state to ensure that a requested power management mode works as expected.

(4) The Windows Kernel Power Manager gets information about specific power management settings from the Windows Power Policy Store (a portion of the Local Machine Registry hive). The Power Manager gets one active plan for the computer—for example “power saver,” “high performance,” or “balanced”—for each of two cases: running when plugged into a power source or on battery.