If automatic power management is enabled by pmconfig or power.conf(4), then all devices with a pm-components(9P) property automatically will use power management. After a component has been idle for a default period, the component is automatically lowered to the next lowest power level. The default period is calculated by the power management framework to set the entire device to its lowest power state within the system idleness threshold.
By default, automatic power management is enabled on all SPARC desktop systems first shipped after July 1, 1999. This feature is disabled by default for all other systems. To determine whether automatic power management is enabled on your machine, refer to the power.conf(4) man page for instructions.
power.conf(4) can be used to override the defaults calculated by the framework.