+
−
+
−-*- mode: outline; coding: utf-8 -*-
+
−
+
−* ACPI power states.
+
−
+
−  http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface
+
−
+
−** Global states.
+
−
+
− * G0 (S0) Working
+
− * G1 Sleeping (subdivides into the four states S1 through S4)
+
−   * S1: All processor caches are flushed, and the CPU(s) stop executing
+
−     instructions. Power to the CPU(s) and RAM is maintained; devices that do
+
−     not indicate they must remain on may be powered down.
+
−   * S2: CPU powered off.
+
−   * S3: Commonly referred to as Standby, Sleep, or Suspend to RAM. RAM
+
−     remains powered.
+
−   * S4: Hibernation or Suspend to Disk. All content of main memory is saved
+
−     to non-volatile memory such as a hard drive, and is powered down.
+
− * G2 (S5) Soft Off. G2, S5, and Soft Off are synonyms. G2 is almost the same
+
−   as G3 Mechanical Off, but some components remain powered so the computer
+
−   can "wake" from input from the keyboard, clock, modem, LAN, or USB device.
+
− * G3 Mechanical Off: The computer's power consumption approaches close to
+
−   zero, to the point that the power cord can be removed and the system is
+
−   safe for dis-assembly (typically, only the real-time clock is running off
+
−   its own small battery).
+
−
+
−** System states.
+
−
+
− * S0 Working (G0), Processor in C0-C3, full context save RAM maintained
+
− * S1 Sleeping with processor context maintained, RAM maintained
+
− * S2 Sleeping with processor content not necessarily maintained, RAM
+
−   maintained, most devices in D3
+
− * S3 Sleeping, lower than S2, RAM maintained, most devices in D3
+
− * S4 Sleeping, lower than S3, RAM not maintained, most devices in D3
+
− * S5 Sleeping, lower than S4, no context saved, reboot necessary
+
−
+
−** Device states.
+
−
+
− * D0 Fully-On is the operating state.
+
− * D1 and D2 are intermediate power-states whose definition varies by device.
+
− * D3 Off has the device powered off and unresponsive to its bus.
+
−
+
−** Processor states.
+
−
+
− * C0 is the operating state.
+
− * C1 (often known as Halt) is a state where the processor is not executing
+
−   instructions, but can return to an executing state essentially
+
−   instantaneously. All ACPI-conformant processors must support this power state.
+
− * C2 (often known as Stop-Clock) is a state where the processor maintains all
+
−   software-visible state, but may take longer to wake up. This processor
+
−   state is optional.
+
− * C3 (often known as Sleep) is a state where the processor does not need to
+
−   keep its cache coherent, but maintains other state. Some processors have
+
−   variations on the C3 state (Deep Sleep, Deeper Sleep, etc.) that differ in
+
−   how long it takes to wake the processor. This processor state is optional.
+
−
+
−** Performance states.
+
−
+
− * P0 max power and frequency.
+
− * P1 less than P0, voltage/frequency scaled.
+
− * Pn less than P(n-1), voltage/frequency scaled.
+
−
+
−* Control power schema under Windows.
+
−
+
−Use powercfg utility. To se current state:
+
−
+
−  cmd> powercfg /QUERY
+
−
+
−To see all available states:
+
−
+
−  cmd> powercfg /LIST
+
−
+
−To restore power configurtion:
+
−
+
−  cmd> powercfg /RestoreDefaultPolicies
+
−
+
−* Intel.
+
−
+
−** Intel Speedstep® Technology.
+
−
+
−  http://www.intel.com/support/processors/sb/CS-028855.htm
+
−                Frequently asked questions for Intel Speedstep® Technology
+
−  http://www.intel.com/p/en_US/support/highlights/processors/frequencyid
+
−                Intel® Processor Frequency ID Utility
+
−  http://software.intel.com/en-us/articles/enhanced-intel-speedstepr-technology-and-demand-based-switching-on-linux
+
−                Enhanced Intel SpeedStep® Technology and Demand-Based Switching on Linux