ThinkWiki - User contributions [en]

ThinkPad Button

2008-06-24T00:14:37Z

Mitoyarzun: /* Models featuring this Technology */

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The ThinkPad Button is a button situated in the upper left corner of the keyboard on modern ThinkPads. It is intended to be a means of quick access to help and support. Technically it is nothing else than a button that can be configured to launch a certain piece of software. While originally it was grey and labelled {{ibmkey|ThinkPad|#494949}}, IBM later made it blue and called it the {{ibmkey|Access IBM|#495988}} Button. Lenovo relabelled it as {{ibmkey|ThinkVantage|#495988}} after it took over the ThinkPad line from IBM.
</div>
|}
__NOTOC__
== System Boot ==
Pressing {{ibmkey|Access IBM|#495988}} or {{ibmkey|ThinkVantage|#495988}} at system boot can launch the [[Predesktop Area| Predesktop Area]]. This depends on a specific setting of the BIOS Setup Utility and on the availability of either a [[Hidden Protected Area|Hidden Protected Area]] or a [[Rescue and Recovery|Rescue and Recovery partition]]. See the linked pages for details.

== Linux support ==
===Using tpb===
Under Linux, the IBM ThinkPad(tm) special keys can be enabled using [[tpb]].

I.e., to make pressing the Access IBM Button launch ntpctl, add the following line {{path|/etc/tpbrc}} file:
THINKPAD /usr/bin/X11/xterm -T ntpctl -e ntpctl

To make pressing the Access IBM Button launch the ThinkWiki homepage in Firefox, add the following line:
<nowiki>THINKPAD /usr/bin/firefox http://www.thinkwiki.org</nowiki>

See the [[tpb]] page and the [[How to get special keys to work | ThinkPad special keys HOWTO]] for more information.

===Using KDE===

KDE supports assigning actions to (some) ThinkPad special keys, through the ThinkPad buttons [[KMilo]] plugin.

It can be activated and configured in the KDE Control Center (<tt>kcontrol</tt>), under <tt>System Administration --> IBM Thinkpad Laptop</tt>.

===Using xbindkeys on Ubuntu===

On Ubuntu (at least 7.04/Feisty) <code>tpb</code> is not really an option, because it conflicts with <code>hotkey-setup</code>, which is responsible for much things working out of the box.

An alternative is to use <code>xbindkeys</code>, which can easily be installed with <code>aptitude install xbindkeys</code> or via the Synaptic package manager. It can be used to assign arbitrary commands to certain keycodes. Therefore, we first have to find this keycode by running <code>xbindkeys --key</code> and pressing the ThinkPad Button. This should result in something like the following:
sean@amalthea ~ $ xbindkeys --key
Press combination of keys or/and click under the window.
You can use one of the two lines after "NoCommand"
in $HOME/.xbindkeysrc to bind a key.
"NoCommand"
m:0x0 + c:159
NoSymbol

Now we can construct a minimal configuration file in <code>~/.xbindkeysrc</code>:
"gnome-terminal"
m:0x0 + c:159
After starting <code>xbindkeys</code> without further options the ThinkPad Button should launch a new terminal.

To start the program automatically at login add it under "System -> Preferences -> Sessions -> Startup Programs" (assuming the Gnome Desktop is used, otherwise add it to your <code>~/.xinitrc</code>, <code>~/.xsession</code> or whatever is responsible for startup items in your setting).

===Using Gnome===

A simpler but less flexible possibility than <code>xbindkeys</code> is "System -> Preferences -> Keyboard Shortcuts". Just go to (for example) "Run a terminal" and press the ThinkPad Button, when asked for a "New accelerator...". This will only work under the Gnome Desktop and cannot execute arbitrary commands, as <code>xbindkeys</code> and <code>tpb</code> can.

== Windows support (2000 or XP) ==
If you want to customize the program that is launched when the {{ibmkey|ThinkPad|#494949}}, {{ibmkey|Access IBM|#495988}} or {{ibmkey|ThinkVantage|#495988}} button is pressed while
the machine is running {{Windows}} (2000 or XP) you can change the following registry entry:

<code>HKEY_LOCAL_MACHINE\SOFTWARE\IBM\TPHOTKEY\8001</code>

Here are the default values for the original IBM version:

[HKEY_LOCAL_MACHINE\SOFTWARE\IBM\TPHOTKEY\8001]
"File"="C:\\Program Files\\IBM\\Access IBM\\aibm.exe"
"DispName"="Access IBM"

And these are the default values for the Lenovo version:

[HKEY_LOCAL_MACHINE\SOFTWARE\IBM\TPHOTKEY\8001]
"File"="C:\\PROGRA~1\\THINKV~1\\PrdCtr\\LPL1.exe"

== Related Links ==
*[[Python script for Windows to control ThinkPad features]] that also allows querying of the ThinkPad button
*[http://www.pc.ibm.com/us/think/thinkvantagetech/accessibm.html IBMs Access IBM ThinkVantage Technology page]
*[http://www-3.ibm.com/pc/support/site.wss/AIBM-TOOLS.html Access IBM - Customization Guide]

==Models featuring this Technology==
'''"ThinkPad" button'''
*ThinkPad {{A Series}}
*ThinkPad {{R30}}, {{R31}}, {{R32}}
*ThinkPad {{T20}}, {{T21}}, {{T22}}, {{T23}}, {{T30}}
*ThinkPad {{X20}}, {{X21}}, {{X22}}, {{X23}}, {{X24}}, {{X30}}
*ThinkPad {{TransNote}}
*ThinkPad {{S30}}, {{S31}}

'''"Access IBM" button'''
*ThinkPad {{G40}}, {{G41}}
*ThinkPad {{R40}}, {{R40e}}, {{R50}}, {{R50e}}, {{R50p}}, {{R51}}, {{R51e}}, {{R52}}
*ThinkPad {{T40}}, {{T40p}}, {{T41}}, {{T41p}}, {{T42}}, {{T42p}}, {{T43}}, {{T43p}}
*ThinkPad {{X31}}, {{X32}}, {{X40}}, {{X41}}, {{X41T}}

'''"ThinkVantage" button'''
*ThinkPad {{R60}}, {{R60e}}, {{R61}}
*ThinkPad {{T60}}, {{T60p}}, {{T61}}
*ThinkPad {{X60}}, {{X60s}}, {{X61}}, {{X61s}}, {{X61_Tablet}}, {{X300}}
*ThinkPad {{Z Series}}

[[Category:Glossary]]

How to reduce power consumption

2008-06-16T16:43:03Z

Mitoyarzun: /* Tools */

Reducing system power consumption will extend battery life, reduce system
temperature and (on some models) reduce system fan noise.
Power consumption can be greatly improved from a stock distribution configuration
to a fine tuned system. The general rules are :
* Unload drivers for unused devices (ie. USB 1.1, Yenta/PCMCIA, Wireless, IRDA, Bluetooth, ...)
* Reduce polling on devices (drives, USB subsystem, nvram, use SATA AN, ...)
* Reduce hard drive activity
* Reduce LCD brightness to the minimum you can stand
* Reduce CPU wakeups, so it can stay longer in deep power saving c-states
* Make use of every hardware devices availables power saving features (AHCI ALPM, USB autosuspend, Alsa and Wireless powersaving modes, HPET timers, ...)

==Tools==
Arjan van de Ven's [[PowerTOP]] utility
is a gold mine to improve energy efficiency, but is almost only CPU-oriented. This tool helps to easily detect
the top power offenders, both userland and kernel modules, which prevent the use of CPU power saving mechanisms and sometime suggest
fixes accordingly.
PowerTOP users collected some [http://www.lesswatts.org/projects/powertop/known.php tips & tricks]
and an informative [http://www.lesswatts.org/projects/powertop/faq.php faq].

Alternatively (or complementary) to PowerTOP, running <code>strace -p $(pidof yourapp)</code>
for all your favorite or background running applications while they are expected to be
idle, will show the misbehaviors.

Beside CPU wakeups, disks spins are also power hungry. To detect what make your disk spinning,

<code>
sysctl vm.block_dump=1
</code>

will list all applications causing disks wakeups on the kernel's dmesg.
Other useful tools for this purpose are blktrace, iostat and lm-profiler
(from laptop-mode-tools suite).

See also [[#Misbehaving Userland]].

==BIOS settings==
Some Thinkpad BIOS (like 2.08 BIOS on {{X40}}) offer two very lame options,
with a very misleading online help (saying "Usually not needed"). That's

<code>
CPU power management: (default disabled)
PCI bus power management: (default disabled)
</code>

You should indeed ''enable'' them, else the deepest C3 and C4 ACPI C-states
are disabled.

==CPU==
Look at:
* [[How to make use of Dynamic Frequency Scaling]]
* [[Pentium M undervolting and underclocking]]

A good thing to keep in mind is that every CPU wakeup, even if it's for
a trivial light job, reduce the time the CPU stays on a deep power
saving C-state (like C3 or C4). Therefore you should ensure your applications
stay really idle when they meant to be idle (track shorts select timeouts
in loop, etc. with [[PowerTOP]]).

Also note that manually locking the CPU in the lowest P-state (frequency)
available is '''not''' an efficient way to improve battery lifetime. This will
cause the CPU to stay longer in C0 (power hungry C-state) doing hard work when
there is something to do, while it could have done this work faster by augmenting
the CPU freq, and returned back faster to a deeper, economic, C-state and to a
lower frequency (P-state).
The best is to let the kernel select the appropriates CPU frequencies by itself
with the help of in kernel CPU governors.
Have a look at [http://www.bughost.org/pipermail/power/2007-May/000166.html this explanation]
from Intel's kernel developer Arjan van de Ven.

==Kernel settings and patches==

===General settings===
The 2.6.21 kernel brought some very effective changes (like [[dynticks]]).
Later, 2.6.24-rc2 brought a lot of other power efficiency improvements.
If it's not already on your distribution and you value power efficiency,
you may think about compiling a recent kernel yourself.

Here are a few options (beside the ACPI and APM related one) that matter to
reduce power consumption or to help diagnosing consumers:

<code>
# From PowerTOP's FAQ:
CONFIG_NO_HZ
CONFIG_HIGH_RES_TIMERS
CONFIG_HPET
CONFIG_HPET_TIMER
CONFIG_CPU_FREQ_GOV_ONDEMAND
CONFIG_USB_SUSPEND
CONFIG_SND_AC97_POWER_SAVE
CONFIG_SND_HDA_POWER_SAVE
CONFIG_SND_HDA_POWER_SAVE_DEFAULT=3
CONFIG_TIMER_STATS
CONFIG_ACPI_BATTERY
CONFIG_CPU_FREQ_STAT
CONFIG_INOTIFY

# Not from the PowerTOP FAQ:
CONFIG_BLK_DEV_IO_TRACE
CONFIG_X86_ACPI_CPUFREQ
CONFIG_X86_SPEEDSTEP_CENTRINO depreciated as of kernel 2.6.24, use CONFIG_X86_ACPI_CPUFREQ
CONFIG_X86_SPEEDSTEP_ICH
CONFIG_X86_SPEEDSTEP_SMI
CONFIG_CPU_IDLE
CONFIG_CPU_IDLE_GOV_LADDER
CONFIG_CPU_IDLE_GOV_MENU
</code>

Those options are already in Fedora Core 7 and Ubuntu Gutsy (not Feisty) default i686 kernels.
PowerTOP FAQ also suggest to '''disable'''
CONFIG_IRQBALANCE and CONFIG_ACPI_DEBUG.

Also, you need to properly set APM and ACPI. Look at:
* [[Power Management]]
* [[How to make use of Power Management features]]

=== Kernel boot and module loading options ===
If you have an Intel chipset > ICH3 (cf. lspci output), as in most modern Thinpads, you should
be using the integrated HPET timer (saves about 30 CPU wake ups per second). To see if
hpet is enabled on your laptop :

<code>
grep hpet /proc/timer_list
</code>

If this does not display "Clock Event Device: hpet", then add

<code>
hpet=force
</code>

to your kernel boot options (usualy in /boot/grub/menu.lst or lilo.conf).
Note that "hpet=force" is only available by default in 2.6.24-rc2 and above
(or as a separated patch for 2.6.22 and 2.6.23, see below).

===Useful Patches===

Thomas Gleixner High Resolution Timers (hrt) patchset brings many improvements,
like the cpuidle work and Udo A. Steinberg and Venki Pallipadi "force
enable HPET" patches (non HPET timers causes about 20-40 CPU wakeups/second, but
HPET is often hidden by the BIOS due to Windows XP deficiencies). Those are
fully merged in 2.6.24-rc1 vanilla kernel.
See http://www.tglx.de/projects/hrtimers/

Kristen Carlson Accardi from Intel has a patchset to turn on "Aggressive
Link Power Management" (ALPM) for the AHCI driver (for SATA bus). Also from
Accardi, SATA Asynchronous Notification (SATA AN), alows SATA link to notify
media insertions (thus avoid hal polling the cdrom). Those patches were merged
in 2.6.24-rc2 kernel (AN needs also support in hal to be used).
See: http://www.kernel.org/pub/linux/kernel/people/kristen/patches/SATA/alpm/

As of now (2.6.24-rc8), the linux kernel doesn't support PCI Express power
management (aka PCIe ASPM, aka PCIe LPM). Shaohua Li from Intel submited a
patch on LKML (http://lkml.org/lkml/2008/1/17/544 ) though, and reported it
to reduce power consumption by 1.3 watts for a system with three PCIe links.

The [[HDAPS]] disk protection systems can reduce battery life.
Matthew Garrett provides [http://www.linuxpowertop.org/patches/hdaps.patch a patch]
that prevents hdaps kernel module to generate interrupts when
this feature isn't used.

===Useful sysctls===
The meaning of those settings is explained case by case on the relevant
sections of this document. But for convenience sake, we group them here too.

Note that the "ondemand" scaling governor is recommended by Intel developers
for energy efficiency: it's expected to be more efficient than the "powersave"
governor, or than userspace daemons (like cpufreq-utils, cpufreqd, powernowd...).
Look [http://www.bughost.org/pipermail/power/2007-May/000071.html here],
[http://www.bughost.org/pipermail/power/2007-May/000073.html here], or
[http://www.bughost.org/pipermail/power/2007-May/000166.html here] for a
kernel developer explanation about "ondemand" being better on modern Intel CPUs.

The "link_power_management_policy" tunable won't be available unless you
run a 2.6.24-rc2 or more kernel, or applied Kirsten patchset, have an Intel
AHCI compatible chipset, and use SATA drives.

<code>
echo 5 > /proc/sys/vm/laptop_mode
echo 0 > /proc/sys/kernel/nmi_watchdog
echo Y > /sys/module/snd_ac97_codec/parameters/power_save
echo 1 > /sys/devices/system/cpu/sched_mc_power_savings
echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo 1500 > /proc/sys/vm/dirty_writeback_centisecs
for i in /sys/bus/usb/devices/*/power/autosuspend; do echo 1 > $i; done
# those sysctl's are only available if you have an AHCI compatible SATA
# controler and use kernel > 2.6.24-rc2 (or use Kristen ALPM patchset) :
echo min_power > /sys/class/scsi_host/host0/link_power_management_policy
echo min_power > /sys/class/scsi_host/host1/link_power_management_policy
</code>

If you're running a kernel older than 2.6.22 do this. Not needed for kernels 2.6.22 onward:

<code>
cd /sys/devices/system/cpu/cpu0/cpufreq
cat ondemand/sampling_rate_max > ondemand/sampling_rate
</code>

==ATA drives==
Hard drives and CDRom drives spinning is very costly. To improve battery
lifetime, you should reduce disks access (or devices polling) the more you
can.

===Hard Drives===
The files access time update, while mandated by POSIX, is causing lots of
disks access; even accessing files on disk cache may wake the ATA or USB
bus. If you don't use this feature, disable it via:

<code>
mount -o remount,noatime / # and so on for all mounted fs
</code>

The laptop_mode reduce disk usage by regrouping writes. You should enable
it, at least while on battery. See [[Laptop-mode]] for more details:

<code>
echo 5 > /proc/sys/vm/laptop_mode
</code>

The default kernel dirty page writeback frequency is very conservative. On
a laptop running on battery, one might find more appropriate to reduce it:

<code>
echo 1500 > /proc/sys/vm/dirty_writeback_centisecs
</code>

Some power saving hard drives features can be activated with hdparm (beware
that "-B 1" may reduce your drive lifetime, if you have lot of intermittent
disk activity causing lots of heads load/unloads: so reduce I/O activity first,
as explained above, in order to get longer disks idling periods).
For more details look at [[How to make use of Power Management features]] :

<code>
hdparm -B 1 -S 12 /dev/sda # and/or any other disk device
</code>

====SATA Link Power Management====
On kernels 2.6.24 and new this enables SATA Link Power Management:
<code>
echo min_power > /sys/class/scsi_host/host0/link_power_management_policy
echo min_power > /sys/class/scsi_host/host1/link_power_management_policy
</code>

Disable it by replacing <code>min_power</code> with <code>max_performance</code>.

On Hardy Heron with a 2.6.24-16 kernel, a suspend/resume cycle is much quicker if you disable SATA Link Power Management before initiating the suspend.

===Optical drive===
The optical drive is reported to consume power even when not accessed. See

* [[How to hotswap UltraBay devices|Eject the UltraBay optical drive]], or just turn off its power supply (i.e., run the appropriate eject script but leave the drive inserted).
* [[How to set optical drive speed|Reduce the spinning speed of the optical drive]].

The hald daemon polling tends to maintain the ATA buses out of power saving
modes, and to wakeup CDROM drive (except if you have a kernel >= 2.6.24, hal >= 0.5.10,
and SATA AN compatible devices). If you have a recent hald version, you
can stop this polling when on battery:

<code>
hal-disable-polling --device /dev/scd0 # or whatever your CD drive is
</code>

start polling again when on ac:
<code>
hal-disable-polling --enable-polling --device /dev/scd0 # or whatever your CD drive is
</code>

If your hald is not recent enough, consider suspending it when running on battery. Some moderns SATA buses and drivers supports a notification mechanism (SATA AN - Asynchronous Events Notifications) that obsolete the need for polling on modern hardware; support for this feature had been merged in Linux 2.6.24-rc1 and HAL 0.5.10.

==LCD Backlight/Brightness==
The LCD backlight is one of the very major power drain.
Reducing brightness to the lowest readable
level will save a lot of battery lifetime. Also, don't forget to configure
your screen saver to shutdown the screen backlight (rather than displaying some
eye candy), when no activity for a few minutes.

You can also let the system [[automatically reduce brightness]] after a
period of inactivity.

If you're choosing your Thinkpad laptop model, keep in mind that the screen
size affect the battery time greatly: more power needed for larger screens.

The very recent, but xorg standard way to control backlight from CLI is
using xbacklight. ie. to set backlight at half the brightness:

<code>
xbacklight -set 50
</code>

You should configure the DPMS to shutdown the screen when idle (rather than
displaying a fancy but power consuming screensaver). ie. to turn off the
display after 5mn of idling:

<code>
xset +dpms
xset dpms 0 0 300
</code>

==Graphic controllers==
All xorg Thinkpad graphics chipsets drivers (ati, radeon, fglrx, i810) have
the same bug causing very frequent CPU wakeups when DRI is activated, even
when you don't use any 3D application.
This problem is partly fixed on xorg git tree but not released as of xorg
7.2. If you value more battery than 3D, you should disable DRI: put this on
the /etc/X11/xorg.conf "Device" of you graphic controller:

<code>
Option "NoDRI"
</code>

Also be sure that DPMS is working: <code>grep DPMS /var/log/Xorg.0.log</code>
should output "DPMS enabled". If not, put <code>Option "DPMS"</code> in your config.
See the section above about how to enable dpms driven display power saving.

On recent xrandr/xorg versions, you can disable the TV output (or any other detected
as connected but not used outputs) when you're not using it: it's known to consume power.

<code>
xrandr # see all displays listed here, but that you don't actually use and disable them.
xrandr --output TV -off # for instance (if "xrandr" above listed a connected output named "TV" that you don't use)
</code>

When you don't have an external monitor plugged, disable CRT and DVI output
(for some, this can make a difference in power usage) :
<code>
echo crt_disable > /proc/acpi/ibm/video
echo dvi_disable > /proc/acpi/ibm/video
</code>

Some drivers have specials power saving mode, and/or allows underclocking the GPU. See also:
* [[How to make use of Graphics Chips Power Management features]], or with [[Rovclock]] on ATI.
* [[Problem with high power drain in ACPI sleep]]

==USB Subsystem==
The kernel support an efficient USB 2.0 power saving feature if you enabled
CONFIG_USB_SUSPEND. This may not trigger in when you have an USB device
plugged (and beside, USB devices tends to suck power on their own), so avoid
using such devices when on battery. To enable it by default, you must add the line
<code>
options usbcore autosuspend=1
</code>
to your <tt>/etc/modprobe.conf</tt> or add it to (and create if necessary) the file <tt>/etc/modprobe.d/usbcore</tt> depending on how your distribution organises modprobe configuratoin.

If on the other hand, you have <tt>usbcore</tt> built into your kernel, you can add this in the kernel boot options (ie. in grub's menu.lst):

<code>
usbcore.autosuspend=1
</code>

or at runtime, per device, with:

<code>
for i in /sys/bus/usb/devices/%s/power/autosuspend; do echo 1 > $i; done
</code>

USB 1.1 is worst. It needs polling the bus frequently, hence can't really go
in a low power mode when you enabled it, even if you don't have any device
plugged. You'd better remove it when you don't use a 1.1 device:

<code>
rmmod uhci_hcd
</code>

If you don't intend to use any device needing USB 1.1 (unfortunately, the built-in bluetooth and fingerprint-reader are USB 1.1 devices), the USB 1.1 support can also be totally avoided. On Debian and derivatives, just do:

<code>
echo "blacklist uhci_hcd" >> /etc/modprobe.d/blacklist
</code>

==PCMCIA/CardBus==
Same for PCMCIA/CardBus. Some users experiences interrupts clouds (sometime up to
several thousands interrupts/second) causing CPU wakeups, thus totally preventing
the CPU to reach lower C-states.
If you don't use PCMCIA, you may disable it the same way (unloading seems insufficient
to restore the system properly, you have to boot without it):

<code>
echo "blacklist pcmcia" >> /etc/modprobe.d/blacklist
echo "blacklist yenta_socket" >> /etc/modprobe.d/blacklist
</code>

==Sound==
ALSA has a power saving feature that should be enabled on your kernel
(CONFIG_SND_AC97_POWER_SAVE). Note that this low power mode won't trigger in
unless you muted all sound inputs (micro, line in etc.). This feature has
to be activated with:

<code>
amixer set Line mute nocap
amixer set Mic mute nocap
echo Y > /sys/module/snd_ac97_codec/parameters/power_save
</code>

More radical: you can unload all sound related modules when you are on
battery, or mute the sound system (echo mute > /proc/acpi/ibm/volume).

See also [[How to enable audio codec power saving]].

==Wireless Interface==
===intel wireless===
Wireless network consume a lot of power.
To save power, you can kill the Wi-Fi radio when it's not in use:

<code>
echo 1 > /sys/bus/pci/devices/*/rf_kill
</code>

If you need Wi-Fi, you can also reduce power consumption (at the price of
performances) by activating the power saving modes:

<code>
iwpriv eth1 set_power 5
</code>

For drivers using the new Wi-Fi kernel framework (mac80211/cfg80211),
the canonical way to do this is now:

<code>
for i in /sys/bus/pci/devices/*/power_level ; do echo 5 > $i ; done
</code>

Most drivers, like ipw2200, that don't use the new mac80211 framework place the
interfaces in aggressive scanning mode when they are not associated with any
Access Point, even when the interface is down (more info about this on Intel's
[http://www.lesswatts.org/tips/wireless.php LessWatts] website).
This behavior consumes a lot of power, even more than when the interface
is plain active and in use. But this can disabled at module's load time :

<code>
rmmod ipw2200
modprobe ipw2200 associate=0
</code>

You can fix this setting by placing the following in /etc/modprobe.d/options
(Debian/Ubuntu) or in /etc/modprobe.conf (Red Hat/Fedora):

<code>
options ipw2200 associate=0
</code>

Reducing beacon intervals on your Access Point to 1 per second will also
reduce network card interrupts, therefore power savings. This shouldn't have
negatives side effects.

See also, to activate power saving on the wireless network card:
* For [[Intel PRO/Wireless 2200BG Mini-PCI Adapter]] and [[Intel PRO/Wireless 2915ABG Mini-PCI Adapter]], see instructions for the [[ipw2200]] driver.
* For [[Intel PRO/Wireless 3945ABG Mini-PCI Express Adapter]], see the [http://ipw3945.sourceforge.net/README.ipw3945 ipw3945 driver README]

==Ethernet Controler==
If you don't use Wake-on-LAN, you should disable it for your network card,
because it sucks a lot of power:

<code>
ethtool -s eth0 wol d
</code>

If you can, try to reduce useless network activity on your ethernet
segment, coming to your NIC (ie. uneeded broadcasts), those cause
interrupts and CPU wakeups.

Forcing 100Mbps full-duplex speed on a gigabit ethernet NIC can also save a lot of power (~1W) on most network workloads. This also reduces components temperature (e.g., [[Thermal Sensors|thermal sensor]] 0xC0 on the {{T43}} cools down by 5 degree between 1000Mbps and 100Mbps, and another 1 degree for 10Mbps).

<code>
ethtool -s eth0 autoneg off speed 100
</code>

Note, however, that if the network device on the other side has auto-negotiation enabled (which is very common) and you turn auto-negotiation off, the other side will assume half-duplex mode and you will experience a significant loss of performance.

==Bluetooth==
When you don't need bluetooth, disable it. Because of its radio,
bluetooth is not power friendly.

<code>
hciconfig hci0 down ; rmmod hci_usb
echo disable > /proc/acpi/ibm/bluetooth
</code>

==Modem==
When was the last time you used your analog modem? If you can't remember, you probably just don't need it. If it is on a separate module in your laptop, simply remove it. Store it in a ESD safe place (like the bag in which your last addon card or hard drive was packed), in case you should need it again. This won't save you a lot of power and weight, but why carry something around you never use.

==System Fans==
Fans consumes power when running, so you may look at the [[ACPI fan control script]].

==Misbehaving Userland==
You should avoid using Beagle, Compiz, Beryl, XMMS, gnome-power-manager
and Evolution while on battery.
Look at the PowerTOP's [http://www.linuxpowertop.org/known.php known problems]
list.

Deactivate desktop animations (blinking cursor on the terms, animated wallpapers, ...): they cause regular X (therefore kernel and CPU) wakeups.

In short, while on battery, you should stop all applications that don't really stay idle when you're not using them. This means applications that:
* Wakes up the CPU too often (by polling something, because of too short select() timeouts, ...)
* Access the disks at regular intervals
* Access an hardware bus (USB, ATA, ...) at regular intervals
To find those offenders run:
* <code>strace -p $(pidof yourapp)</code> # for all your running applications
* <code>powertop</code>
* <code>sysctl vm.block_dump=1</code> # and look at dmesg
* <code>ps aux | awk '{print$10,$11}' | sort -n</code> # will list all running softs sorted by used cpu time
Please, don't forget to fill a bug when you find such a misbehaving software.
{{NOTE|Not all software is evil, buggy or badly written. Some produce regular activity because they have to, in order to provide their intented functionality. Think twice before filling bugs about this.}}

==See Also==
* [[How to measure power consumption]]
* [[Script for monitoring power consumption]]
* Battery [[maintenance]]

==External resources==
* [http://www.free-it.de/archiv/talks_2005/paper-11017/paper-11017.html ''Current trends in Linux Kernel Power Management''], Dominik Brodowski, 2005
* [http://www.linuxpowertop.org PowerTOP] website
* [http://www.gentoo.org/doc/en/power-management-guide.xml Power Management Guide] from the Gentoo Linux documentation
* [http://mailman.linux-thinkpad.org/pipermail/linux-thinkpad/2005-November/030478.html When/where/what for low power consumption?] (thread on Linux-Thinkpad)
* Intel's [http://www.lesswatts.org/ LessWatts] "''Saving power on Linux''" website
* ''8 hours of battery life on your lap(top)'' ([http://atrey.karlin.mff.cuni.cz/~pavel/swsusp/8hours.odp ODP]/[http://atrey.karlin.mff.cuni.cz/~pavel/swsusp/8hours.pdf PDF]), a presentation by Pavel Machek

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