Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual page 532

/proc/acpi/thermal_zone/*/state
The state indicates if everything is ok or if ACPI applies active or passive
cooling. In the case of ACPI-independent fan control, this state is always ok.
/proc/acpi/thermal_zone/*/cooling_mode
Select the cooling method controlled by ACPI. Choose from passive (less perfor-
mance, economical) or active cooling mode (full performance, fan noise).
/proc/acpi/thermal_zone/*/trip_points
Enables the determination of temperature limits for triggering specific actions, like
passive or active cooling, suspension (hot), or a shutdown (critical). The
possible actions are defined in the DSDT (device-dependent). The trip points deter-
mined in the ACPI specification are critical, hot, passive, active1, and
active2. Even if not all of them are implemented, they must always be entered
in this file in this order. For example, the entry echo 90:0:70:0:0 >
trip_points sets the temperature for critical to 90 and the temperature
for passive to 70 (all temperatures measured in degrees Celsius).
/proc/acpi/thermal_zone/*/polling_frequency
If the value in temperature is not updated automatically when the temperature
changes, toggle the polling mode here. The command echo X >
/proc/acpi/thermal_zone/*/polling_frequency causes the temper-
ature to be queried every X seconds. Set X=0 to disable polling.
None of these settings, information, and events need to be edited manually. This can
be done with the Powersave daemon (powersaved) and its various front-ends, like
powersave, kpowersave, and wmpowersave. See Section 28.3.3, "ACPI Tools"
(page 516).
28.3.2 Controlling the CPU Performance
The CPU can save energy in three ways. Depending on the operating mode of the
computer, these methods can be combined. Saving energy also means that the system
heats up less and the fans are activated less frequently.
Frequency and Voltage Scaling
PowerNow! and Speedstep are the designations AMD and Intel use for this tech-
nology. However, this technology is also applied in processors of other manufac-
514 Installation and Administration