could somebody tell me why the hell my laptop with windows lasts for 2 and a half hours fully charged and linux lasts for 1 and a half hour?? without ACPI and the likes??

Im not recommending it, but using the 2.6 kernel, Im getting about 1/2 hour more using linux than it did with Windows, wtih ACPI and APM enabled by using very conservative settings, blanking the screen, power down the harddive, ect. I get about 3 1/2 hrs on a fully charged battery. The 2.6 kernel has all thouse options built in. There are patches for the 2.4.xx kernels that will do the same thing.

I've just gone through this whole nightmare trying to get things to work myself. The thing is ACPI might not be reckognizing your processor and it isn't throttling the cpu to save power. This also results in a very hot laptop and a fan that constantly runs (if the laptop is relatively fast).

You didn't specify what type of a laptop you have but if it is relatively new and has a mobile processor then the laptop is designed to scale the CPU frequency according to use. In Linux the scaling is done either by ACPI or Cpufreq. If you have a Mobile Athlon XP that is a 2400 or more post back because there is a trick to getting this thing to work.

Try the following command in a terminal

cat /proc/acpi/processor/CPU0/info

You should get something like:

processor id: 0
acpi id: 0
bus mastering control: yes
power management: yes
throttling control: no
performance management: no
limit interface: no

Notice on mine how throttling control is no. This means that acpi isn't reckognizing the processor and thus isn't scaling the processor speeds and saving power. If this is the case as it was for me you should consider moving on to using cpufreq.

Cpufreq has to be compiled into the kernel to work so if you haven't done a compile yet you might want to figure out that process first. When compiling the kernel you will select Cpufreq and what driver to be used for your processor.

When Cpufreq is in the kernel you then have to load the module for your processor. The module provides access to the cpu to change the frequency. Then it is a matte of getting a program like cpufreqd or cpuspeed that will access cpufreq and scale the processor speed automatically.

When I first moved to Mandrake I would get maybe 45 minutes on battery life. Through a lot of time spent banging my head I now have my laptop to around 3 hours of battery life. You can do it, just keep learning.

Thanks for the above comment adamis!!

well... my laptop is an ASUS L3500D with an AMD Atlhon XP 2000+

You think it might work anyway? what you said above??

If so i would GREATLY apreciate it!!

Is your laptop a mobile processor? IE my laptop is an Athlon XP-M. You need a mobile chip in order to take advantage of clock scaling. You can see if cpufreq is already built into the kernel and reckognizes your processor by typing the following into a konsole:

cat /proc/cpufreq

If it gives you something like:

minimum CPU frequency - maximum CPU frequency - policy
CPU 0 532000 kHz ( 29 %) - 1795500 kHz (100 %) - userspace

Then you are set. You just need to find a program that will scale the processor for you. Try cpuspeed or cpufreqd. One or the other will do what you want. I'd start with cpuspeed as it is a little easier to install. It's made by carlthompson or something.

Also, if you get something that looks like the above info you can type the following into a konsole to throttle the cpu manually. Just one note, you can't jump down to the minimum speed right way. You have to step down.

as root in a konsole type:

echo "0:1200000:1200000:powersave" >/proc/cpufreq
echo "0:500000:500000:powersave" >/proc/cpufreq

note the 500000 is the minimum supported speed by my processor, your's might be different. There might be a possibility of the cpu freezing if you take to big of a jump or throttle the cpu to something it doesn't support.

Hi,

could you help me?
I've a mobile Athlon 4 and I'd like to use a Slackware 10.2 with it. But the fan it's very noisy - working so much.
I use windows too, and the fan works very well, without noise.
I tried to recompile the kernel 2.6.16.2 in the Slackware 10.2 to support ACPI and CPU freq buit-in, without results. With only APM the results it's the same.
I tried to patch the kernel with modules to other mobile architeture (modules in AMD's site), but the problems continue.
I tried to install cpuspeed, cpufreqd, cpufrequtils-xxx, with no results.
There's suport in the Slackware 10.2 to my PC? What I'm doing wrong?