APM Advanced Power Management

• Advance Power Management (APM) was created by Microsoft in conjunction with Intel in 1993.
• It is a BIOS-level programming interface between the hardware and the operating system (OS).
• APM uses a layered approach to power management.
• Power States:
• Full On
• This is the normal working operation.
• APM Enabled
• APM is available if needed.
• All devices are working at full power consumption but can be powered down if not in use.
• The CPU clock may be slowed down or stopped
• Standby
• Most devices are in a minimal power state.
• The system state is saved to RAM.
•  Recovery is quick (near instantaneous).
• Suspend
• Most devices are powered off.
• The CPU clock is off.
• The system state is saved to disk.
• Recovery is slow.
• Hibernation
• Hibernation is a "special implementation of the AMP Suspend state."
• The system state is saved to the non-volatile hard drive.
• The computer is powered down.
• The BIOS must start up with POST.
• Off
• Computer is powered down and inactive.
• The system state is not necessarily stored.
• The system must go through the entire boot process to start up.
• APM has been replaced by ACPI (Advanced Configuration and Power Interface).