12.3. CPU

12.3.1.1. SpeedStep Tool

    model name : Intel(R) Pentium(R) III Mobile CPU 1000MHz

    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 .

12.3.1.3. 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.

12.3.1.4. SONY VAIO SPIC Daemon

The SONY VAIO SPIC daemon is a fast and small hack to create a working apmd to Sony VAIO laptops. It uses the sonypi kernel module to detect the AC adapter status and the LCD backlight, and cpufreq for CPU frequency scaling.

12.3.1.5. CPUIDLE

A software utility that will make your CPU run cooler? Sounds pretty strange, huh? Let me explain: Have you ever thought of the fact that your CPU is idle most of the time when you're using your computer? For example, when you're using your word processor, writing emails, browsing the web, the CPU does nothing else than just wait for user input. In fact, it will use up to 30W and produce substantial amounts of heat doing nothing. Good operating systems, like Linux, NT and OS/2 have a so-called "idle loop" - a loop that's always executed when the CPU has nothing to do. This loop consists of halt (HLT) instructions. CPUs like the AMD K6, the Cyrix 6x86 and 6x86MX have a special feature called "suspend-on-halt". This means that everytime the CPU executes a hlt instruction, it will go into "suspend mode" for a short time. So, while the idle loop is being executed, the CPU will be in suspend mode, use much less power, and stay much cooler. Of course, this does not affect performance at all! The user won't even notice that his CPU is in suspend mode most of the time (unless he touches the heatsink).

12.3.1.6. autospeedstep

autospeedstep is a daemon that controls power consumption and processor speed depending of the CPU load. It works with Intel Speedstep CPUs and Linux kernels running the 2.5 ACPI backport.

12.3.1.7. ACPI

 #! /bin/sh

# /etc/init.d/slowcpu: slow down cpu or accelerate it via speedstep

test -e /proc/acpi/processor/CPU0/performance || exit 0

case "$1" in
    start)
    echo "Setting CPU0-Speed to: 733 MHz."
    echo 1 > /proc/acpi/processor/CPU0/performance
	;;
    stop)
    echo "Setting CPU0-Speed to: 1133 MHz."
    echo 0 > /proc/acpi/processor/CPU0/performance
	;;
    force-reload|restart)
	;;

    *)
	echo "Usage: $0 {start|stop}"
	exit 1
esac

exit 0