ACPI Power States [Note]

ACPI Power States

Global Power States

Global system states (Gx states) apply to the entire system and are visible to the user.

G3 Mechanical Off

A computer state that is entered and left by a mechanical means (for example, turning
off the system’s power through the movement of a large red switch). It is implied by
the entry of this off state through a mechanical means that no electrical current is
running through the circuitry and that it can be worked on without damaging the
hardware or endangering service personnel. The OS must be restarted to return to the
Working state. No hardware context is retained. Except for the real-time clock, power
consumption is zero.

G2/S5 Soft Off

A computer state where the computer consumes a minimal amount of power. No user
mode or system mode code is run. This state requires a large latency in order to return
to the Working state. The system’s context will not be preserved by the hardware. The
system must be restarted to return to the Working state. It is not safe to disassemble
the machine in this state.

G1 Sleeping

A computer state where the computer consumes a small amount of power, user mode
threads are not being executed, and the system “appears” to be off (from an end user’s
perspective, the display is off, and so on). Latency for returning to the Working statevaries

on the wake environment selected prior to entry of this state (for example,
whether the system should answer phone calls). Work can be resumed without
rebooting the OS because large elements of system context are saved by the hardware
and the rest by system software. It is not safe to disassemble the machine in this state.

G0 Working

A computer state where the system dispatches user mode (application) threads and
they execute. In this state, peripheral devices (peripherals) are having their power state
changed dynamically. The user can select, through some UI, va