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My laptop CPUs are throttled down to .8GHz instead of 2.5GHz whenever I am connected to AC only and not the battery. I tried using cpufreq-set and it allows me to set the speed when the battery is connected but it stays at a maximum of .8GHz when the battery is disconnected. Is there a way to prevent this?

Update: I've also tried changing the governor, but it seems locked at .8GHz whenever it's on only AC power. Are there any overrides for this?

Vreality
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  • This will solve all your problem ... use powersave on ac/bat http://askubuntu.com/questions/285434/jupiter-or-similar-power-saving-app-for-13-04/285681#285681 – Qasim May 16 '13 at 12:27
  • @Qasim That looks like a great tool and I'm liking it already, but sudo tlp ac still has the CPUs at .8GHz if I take out the battery. Could this be a BIOS or kernel issue? – Vreality May 17 '13 at 09:34
  • .8 mean running on 800 MHz & thats 100 % fine ...you can change it with cpu freq indication ...see just after TLP settings ...you don’t need to > sudo tlp ac < , removing battery ...that i would say dont do that ...cauzz if ac power is disconnected you have change of data corruption ...talking the battery out and running on ac power no issue ... i have done several time no issue ...but its dangerous .. – Qasim May 17 '13 at 09:56
  • @Qasim I don't really understand the beginning of your comment, but it works fine on AC only (not battery); it's just slow. The point is, I want to be able to run CPU intensive programs on only AC power so that I don't mess up my battery. I'm okay with the data loss risk; power outages/resets are rare where I live. – Vreality May 17 '13 at 10:22
  • use 3.) Processor and Frequency Scaling > ondemand < on both ac/bat .. – Qasim May 17 '13 at 10:33
  • I set both to ondemand and then performance but neither worked. – Vreality May 17 '13 at 12:23
  • check my answer http://askubuntu.com/questions/296653/ubuntu-13-04-cpu-frequency-scaling-stuck-on-lowest-frequency i hope it will help you – Qasim May 17 '13 at 12:27
  • @Qasim I've changed the governor, but it still does not work. I'm using lscpu to determine the frequency. – Vreality May 17 '13 at 14:30
  • same here cpu is scaling but lscpu showing 800 – Qasim May 17 '13 at 14:34

2 Answers2

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CPU scaling is controlled by your BIOS and not by the software running on the computer.

Reboot and go into the BIOS configuration.

Look for an item called "CPU scaling" and toggle it.

If it's not there, you can't prevent that from happening.

Majik
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  • Thank you! This makes sense, but I don't think my BIOS has that option... Do you know why the BIOS has this option? – Vreality Aug 27 '13 at 12:32
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That is only the operating system (and drivers themsevelves) honor it. I've specificaly disabled "SpeedStep" in my bios and still have to tell the kernel post-boot in userland to not honor these controls. Hope it saves someone a day.

Matthew Brandon Davis
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