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Sunday, June 21, 2009

Running laptop cool and long with Ubuntu, without it getting hot

I am reading interesting posts in Linux kernel mailing list about kernel timer frequency. It is generally like this

There are four kernel timer frequencies (other than this any frequency can be given by editing the code directly, these are the preset frequencies)

1. 100 Hz --> very good for servers as the timer frequency is low, server can run long enough and draw very less power, also all windows have 100 Hz as their kernel timer frequency, so it gives more power saving and reason it gives more battery time in laptops, since some companies use cheap capacitors which are tested only in 100 Hz config, any higher frequency can make them buzz with noise, running a OS with 100 Hz as a guest in virtualization makes the overall system run more stable

2. 250 Hz --> almost twice as fast as 100 Hz and also gives good power saving, Ubuntu, Linux Mint and Debian use this by default

3. 300 Hz --> faster than 250 Hz, gives good power saving, and very good media playback, it is very good for watching high quality videos, Arch Linux kernel uses this by default and watching movies in Arch Linux is a pleasure. Also since the timer frequency is more, Arch Linux feels faster than Ubuntu (and of course, Arch Linux is optimized for i686 and uses a low latency kernel (a hard preemptive kernel))

4. 1000 Hz --> faster than any preset frequency (in kernel configuration) and gives an interrupt of 1 ms timer approx, and very good for playing games, watching HD (High Definition) movies, editing multimedia, but very bad for power saving in your laptop, and can heat laptop considerably, but very good as a host for running virtualization. This is the default kernel timer frequency used by Fedora and considered as a good virtualization host

How to change default kernel frequency in Ubuntu?

We can install a different kernel and get a different kernel frequency. In general server kernels use lowest kernel timer frequency and desktop kernels go with higher kernel frequencies

To get very less heat, run longer and more stable, but a little slower than current Ubuntu, you can install

install from synaptic linux-server

or if you are in Ubuntu


To get very fast and snappy system (for watching movies, playing games, editing multimedia content and getting applications open/run very fast) and as a good host for virtualization, you can try running Fedora or in Ubuntu

install from synaptic linux-rt

or if you are in Ubuntu


To run Ubuntu as a guest in virtualized environment (inside VMWare, VirtualBox, qemu or inside any other virtualization program) there is a special optimized kernel.

install from synaptic linux-virtual (only install this kernel in the Ubuntu running inside your VirtualBox or VMWare or qemu)

or if you are in Ubuntu

Use this only for Ubuntu running as a guest linux-virtual

you can read more about kernel frequency by searching

After installing any new kernel reboot and boot with your newly installed kernel to see the change. And if there is a problem, continue with the default kernel


  1. Hi

    Actually Fedora uses 1000Hz by default.

  2. Yes true, that is what I wrote under 1000Hz --> ... This is the default kernel timer frequency used by Fedora and considered as a good virtualization host