23
Power Management
Power management is especially important on laptop computers, but is also useful on
other systems. ACPI (Advanced Conguration and Power Interface) is available on all
modern computers (laptops, desktops, and servers). Power management technologies
require suitable hardware and BIOS routines. Most laptops and many modern desktops
and servers meet these requirements. It is also possible to control CPU frequency scaling
to save power or decrease noise.
23.1 Power Saving Functions
Power saving functions are not only signicant for the mobile use of laptops, but also
for desktop systems. The main functions and their use in ACPI are:
Standby
not supported.
Suspend (to memory)
This mode writes the entire system state to the RAM. Subsequently, the entire
system except the RAM is put to sleep. In this state, the computer consumes very
little power. The advantage of this state is the possibility of resuming work at the
same point within a few seconds without having to boot and restart applications.
This function corresponds to the ACPI state S3. The support of this state is still
under development and therefore largely depends on the hardware.
Power Management 421
