33.2. APM

Some of the power saving functions are performed by the APM BIOS itself. On many laptops, standby and suspend states can be activated with key combinations or by closing the lid without any special operating system function. However, to activate these modes with a command, certain actions must be triggered before the system is suspended. To view the battery charge level, you need special program packages and a suitable kernel.

SUSE Linux kernels have built-in APM support. However, APM is only activated if ACPI is not implemented in the BIOS and an APM BIOS is detected. To activate APM support, ACPI must be disabled with acpi=off at the boot prompt. Enter cat /proc/apm to check if APM is active. An output consisting of various numbers indicates that everything is OK. You should now be able to shut down the computer with the command shutdown -h.

BIOS implementations that are not fully standard-compliant can cause problems with APM. Some problems can be circumvented with special boot parameters. All parameters are entered at the boot prompt in the form of apm=parameter. parameter is one of:

on or off

Enable or disable APM support.

(no-)allow-ints

Allow interrupts during the execution of BIOS functions.

(no-)broken-psr

The “GetPowerStatus” function of the BIOS does not work properly.

(no-)realmode-power-off

Reset processor to real mode prior to shutdown.

(no-)debug

Log APM events in system log.

(no-)power-off

Power system off after shutdown.

bounce-interval=n

Time in hundredths of a second after a suspend event during which additional suspend events are ignored.

idle-threshold=n

System inactivity percentage from which the BIOS function idle is executed (0=always, 100=never).

idle-period=n

Time in hundredths of a second after which the system activity is measured.

The APM daemon (apmd) is no longer used. Its functionality is now handled by the new powersaved, which also supports ACPI and provides many other features.