How can I underclock my Laptop for greater battery life?

Romanus81 · 12-02-2008, 01:49 PM

I have an 1.6GHz Intel Atom CPU in my MSI Wind and I would like to be able to underclock it, so that while I'm just doing some coding or typing a paper for school, I can make my battery last a bit longer.
Does slackware have tools built in to over/underclock my CPU, or do I need to be enable something in my kernel?
Thanks for any help anyone can give me on this topic.

Ilgar · 12-02-2008, 02:42 PM

Here are a couple of threads from this forum where you can find information on cpufreqd:

http://www.linuxquestions.org/questi...laptop-675183/

http://www.linuxquestions.org/questi...ttling-617741/

You can also directly use the /sys interface. For example on my computer I have created a rather simple script file /usr/local/bin/cpuspeed with content

Code:

echo $1 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

and at startup (in /etc/rc.d/rc.local) I call

/usr/local/bin/cpuspeed ondemand

to switch to ondemand. If I need anything else I can do

Code:

# cpuspeed performance
# cpuspeed powersave

to switch to another governor. Ondemand is the one which reduces the clock speed when the cpu is idle (and increases when there is demand).

dive · 12-02-2008, 02:50 PM

You might also want to look at powernowd - it keeps your cpu at the lowest speed until needed to step up.

dugan · 12-02-2008, 03:15 PM

I think this is the most recent thread about it:
http://www.linuxquestions.org/questi...edstep-684852/

rworkman · 12-02-2008, 11:58 PM

The power management guys say to use the ondemand frequency governor - period - don't bother with all the userspace control mechanisms.

dive · 12-03-2008, 01:58 AM

From rc.local:

Code:

/bin/echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

statguy · 01-10-2009, 03:08 PM

I just found this thread, very useful.

I have now set my laptop to use ondemand as per the suggestion. My question is will this give the best battery life or should I also use a powersave governor and switch to that while on battery?

ErV · 01-10-2009, 05:10 PM

Quote:

Originally Posted by Ilgar

Code:

echo $1 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor

and at startup (in /etc/rc.d/rc.local) I call

/usr/local/bin/cpuspeed ondemand

to switch to ondemand. If I need anything else I can do

Code:

# cpuspeed performance
# cpuspeed powersave

to switch to another governor. Ondemand is the one which reduces the clock speed when the cpu is idle (and increases when there is demand).

This will work for single-core cpus only.
I recommend to read this: http://slackwiki.org/CPU_Frequency_Scaling

guanx · 01-10-2009, 05:19 PM

Fixed.