12.3.1. SpeedStep
Speedstep is a feature of recent CPUs made by Intel, which lets you set CPU frequency. There are different Linux tools to get this to work. Similar features are also available for other CPUs from AMD or the StrongARM CPU, I will describe this in a later issue (assistance welcome).
Before configuring SpeedStep have a look into the BIOS options.
12.3.1.1. SpeedStep Tool
The SpeedStep tool works with Mobile Pentium-III CPUs only. See output from cat /proc/cpuinfo :
model name : Intel(R) Pentium(R) III Mobile CPU 1000MHz
It does not work with the mobile version of the Pentium-III:
model name : Pentium III (Coppermine)
12.3.1.2. CPUFREQ
You might want to check into the cpufreq patch for the linux-2.4/2.5 kernels, maybe it works for your machine: CPU clock frequency scaling for Linux, on x86 and ARM based processors. This module provides a user-space and standard kernel-space interface to this feature, along ARM system-on-a-chip devices to cope with processor clock changes. Since the power consumed by a processor is directly related to the speed at which it is running, keeping the clock speed as low as possible allows you to get more run-time out of your battery. Some people use this to adjust their clock speed many times a second to optimise performance vs battery life. See also the CVS repository .
12.3.1.2.1. cpufreqd
cpufreqd is meant to be a replacement of the speedstep applet you can find on some other operating systems, it monitors battery level, AC state and running programs and adjusts the frequency governor according to a set of rules specified in the config file. It works both with APM and ACPI.
12.3.1.2.2. cpudyn
cpudyn controls the speed in Intel SpeedStep and PowerPC machines with the cpufreq compiled in the kernel. It saves battery and lowers temperature, without affecting the performance of interactive applications.
12.3.1.2.3. cpuspeedy
cpuspeedy allows you to change the clock speed and voltage of CPUs using Linux's CPUFreq driver. It is a user space program, so it will work on every processor supported by the kernel's CPUFreq driver.
12.3.1.2.4. powernowd
PowerNowd is a simple client daemon for the Linux cpufreq driver using the sysfs interface. It sits in the background and changes CPU speed in configurable "steps" according to usage. Written in C, its emphasis is on speed and simplicity. It is very configurable, and supports non-x86 and SMP systems.
12.3.1.3. Laptop Mode
Laptop mode is a kernel "mode" that allows you to extend the battery life of your laptop. It does this by intelligently grouping write activity on your disks, so that only reads of uncached data result in a disk spinup. It has been reported to cause a significant improvement in battery life (for usage patterns that allow it).
The Laptop Mode Tools package spins down your hard drive like noflushd, but it works also on journalling filesystems. It integrates with apmd/acpid/pbbuttonsd to enable this behaviour only when you are running on battery power. It also adjusts some hdparm settings and remounts your filesystems noatime, and it can adjust your maximum CPU frequency.
* License
