ACPI

Advanced Configuration and Power Interface
latest version is 3.0b
key element in Operating System-directed configuration and Power Management(OSPM)
ACPI has its own language called ACPI Machine Language(AML), which is interpreted by the OS
ACPI requires compliant hardwares

Global State
G0(S0) : working
normal working state
G1 : sleeping, subdivided into 4 sub-states
S1 : all processor caches are flushed.
CPU stop executing instructions.
power to CPU and RAM is maintained.
S2 : deeper sleep state than S1.
CPU power is off.
S3 : standby in windows, sleep in mac, also known as suspend to RAM(STR).
powered : RAM
S4 : hibernation in windows, safe sleep in mac, also known as suspend to disk
G2(S5) : soft off
需要重新啟動系統
G3 : mechanical off
only the real-time clock is running