cpu scaling frequency limited when on ac power

[Damir3004]

Binary package hint: powermgmt-base

I am running Ubuntu 10.10 64-bit on my laptop (i7 720qm 1.6 GHZ).

The short story: when I am on AC, these settings are active:
governor: ondemand
cpu scaling range: 933 MHz - 1.47 GHz

When I unplug the AC chord, these (correct) settings become active:
governor: ondemand
cpu scaling range: 933 MHz - 1.60 GHz

The bug is that I cannot set my upper frequency value to 1.6 GHz when I am on power.
I have tried different tools (also removing them all) with no luck.
I found a forum post (http://ubuntuforums.org/showthread.php?t=1077234) where the same problem is encountered. The conclusion was that the BIOS needed an update. I have tried all versions of the BIOS for my laptop, no luck. What is exactly the dependence on the BIOS for cpu scaling (related to unplugging and plugging in the AC power chord)?

I also reported this problem on the Ubuntu forum:
http://ubuntuforums.org/showthread.php?t=1716329

[Damir3004 (damir3004)]

The problem is actually very serious as I found that Turbo Boost is also affected by it.
When I render a Blender scene with 1 thread, 1 cpu is active with 1.47 GHz (no Turbo Boost!).
If you work on battery, 1 cpu is active with 2.8 GHz (Turbo Boos kicks in!)

I do not know if other people experience the same thing (you only notice it when you try cpu scaling for yourself).

[Damir3004 (damir3004)]

I am not the only one, this one is from 2008: http://ubuntuforums.org/showthread.php?t=904748
The problem is still not solved, I would say that this is a rather urgent problem for laptop users because one cannot use his/her laptop to the fullest while on ac with Ubuntu!

[Damir3004 (damir3004)]

I also found that the power supply can be the problem (I have a mobile power supply, 90W). I will test it as soon as I can with a normal power supply. But still, this should be fixed, right?
http://ubuntuforums.org/showthread.php?t=823299

[Damir3004 (damir3004)]

I don't know if this bug can be closed (I think so) because this is really related to the BIOS and maybe to the power supply. I just checked and I can confirm that I get the same behavior under Windows 7 x64. I think it is the power supply, very strange.

[maulynvia (mervynlovatt)]

I think I have the same issue. See my posts http://ubuntuforums.org/showthread.php?t=1793637 and http://ubuntuforums.org/showthread.php?t=1792945

(Ubuntu 10.4 on 32 Bit)

[Damir3004 (damir3004)]

I found actually that this is not a bug, but a hardware limitation... my i7
processor needs the power from the ac (120W) to run turbo boost and higher
frequencies..
On Jul 3, 2011 11:51 PM, "maulynvia" <email address hidden> wrote:
> I think I have the same issue. See my posts
> http://ubuntuforums.org/showthread.php?t=1793637 and
> http://ubuntuforums.org/showthread.php?t=1792945
>
> (Ubuntu 10.4 on 32 Bit)
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/744429
>
> Title:
> cpu scaling frequency limited when on ac power
>
> Status in “powermgmt-base” package in Ubuntu:
> New
>
> Bug description:
> Binary package hint: powermgmt-base
>
> I am running Ubuntu 10.10 64-bit on my laptop (i7 720qm 1.6 GHZ).
>
> The short story: when I am on AC, these settings are active:
> governor: ondemand
> cpu scaling range: 933 MHz - 1.47 GHz
>
> When I unplug the AC chord, these (correct) settings become active:
> governor: ondemand
> cpu scaling range: 933 MHz - 1.60 GHz
>
> The bug is that I cannot set my upper frequency value to 1.6 GHz when I am
on power.
> I have tried different tools (also removing them all) with no luck.
> I found a forum post (http://ubuntuforums.org/showthread.php?t=1077234)
where the same problem is encountered. The conclusion was that the BIOS
needed an update. I have tried all versions of the BIOS for my laptop, no
luck. What is exactly the dependence on the BIOS for cpu scaling (related to
unplugging and plugging in the AC power chord)?
>
> I also reported this problem on the Ubuntu forum:
> http://ubuntuforums.org/showthread.php?t=1716329
>
> To manage notifications about this bug go to:
>
https://bugs.launchpad.net/ubuntu/+source/powermgmt-base/+bug/744429/+subscriptions

[Phillip Susi (psusi)]

Closing per reporter request.