This article describes the different Advanced Power Management (APM)
The Advanced Power Management (APM) Specification defines the following power states:
Three of these states apply both to individual computer components and to
your computer as a whole. The suspended state is a special low power
condition that applies to your computer as a whole, and not the individual
In the ready state, your computer or device is fully powered up and ready
for use. The APM definition of Ready only indicates that your computer or
device is fully powered on, it does not differentiate between active and
Stand-by is an intermediate system-dependent state which attempts to
conserve power. Stand-by is entered when the Central Processing Unit(CPU)
is idle and no device activity is known to have occurred within a specific
period of time. Your computer will not return to ready until one of the
following events occur:
- A device raises a hardware interrupt
- Any controlled device is accessed
All data and operational parameters are preserved when your computer is in
the Stand-by state.
The Suspended state is a computer state which is defined to be the lowest
level of power consumption available that preserves operational data and
parameters. The suspend state can be initiated by either the system Basic
Input Output System (BIOS) or the software above the BIOS. The system BIOS
may place your computer into the suspended state without notification if
it detects a situation which requires an immediate response such as the
battery entering a critically low power state. When your computer is in
the Suspended state, computation will not be performed until normal
activity is resumed. Resumption of activity does not occur until signaled
by an external event such as a button press, timer alarm, and so on.
Windows Millennium Edition has built in support for hibernation (OS-controlled ACPI S4 sleep state). Hibernation saves the complete state of the computer and turns off the power. The computer appears to be off. This is the lowest power sleeping state available and is secure from power outages.
When you resume from a hibernated sleep state, the BIOS performs the normal POST, and then reads the hiberfile that was created to save the computer state. The computer returns to the last state it was in before the computer entered hibernation mode.
Hibernate mode reduces start time.
Note that when you service the computer, make sure you shut down the computer instead of using hibernate mode.
Windows Me supports Hibernate capabilities (ACPI S4 sleep state). Windows Me S4OS Hibernate is available on new computers and upgrades that meet the requirements for the correct video drivers and no VXD audio drivers.
S4 is the hibernation state. It is very close to the APM Suspend to Disk state.
Computer must support APM 1.2, or ACPI.
A paging device that supports D3 (note - certain SCSI configurations do not support this).
No legacy capture devices connected.
WebTV for Windows is not installed.
Non-ICS Host (client is OK).
When in the Off state, your computer or device is powered down and
inactive. Data and operational parameters may or may not be preserved in
the Off state.
If you use Windows Vista, you can visit the following Microsoft Web page for help with power consumption and battery life problems:
APM 1.0 Specification, Microsoft Windows 98 Resource Kit
for other considerations.