Why does the Advanced Power Management (APM) tab appear in the Control Panel Power Options applet on only some of my machines?

A. Windows uses APM when Advanced Configuration and Power Interface (ACPI) isn't available because of hardware limitations. For APM to be available, the computer must support APM 1.2 and not be listed in the Disable APM list in the biosinfo.inf file that the system checks during installation. Also, keep in mind that

  • APM isn't available on multiprocessor machines.
  • Server products don't support APM.
  • You must enable APM in the computer BIOS before APM will appear as an option in Windows.

You can check the APM status of your Windows XP and later machine by performing the following steps:

  1. Start a command session.
  2. Enter the command
    apmstat -v 

Your computer will display its APM status. For example, when you type this command on an ACPI-enabled machine, the command will return the following result:

This is an ACPI machine, APM is NOT relevant on this machine
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