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I have observed a problem with Ubuntu 13.04. The problem was not there on 11.10 I used earlier. The maximum CPU frequency is stuck at 2GHzon my Intel(R) Core(TM) i7-2620M CPU @ 2.70GHz (Dell Lattitude E6320)

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies 
2701000 2700000 2400000 2200000 2000000 1800000 1600000 1400000 1200000 1000000 800000

# echo 2700000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 

I can set scaling_max_freq to a lower value and that works. I can also go back to 2GHz, but not more than that:

# echo 800000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 

# echo 2000000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 

# echo 2200000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 

Nothing I do seems to help - I have installed TLP, uninstalled it, checked different kernel versions available in 13.04. I have attached and removed the power supply. I have changed the governors and also used the userspace. Regardless of whether I am on AC or battery, the above problem persists.

I have seen people having similar problems before (here, or here), but that was related to a kernel bug back in 2008 and does not seem to be relevant.

Does anyone know how to fix this?

share|improve this question
up vote 17 down vote accepted

The problem was identical to that described on this blog - the BIOS was limiting my CPU frequency, or at least suggested that Linux limits it:

# cat /sys/devices/system/cpu/cpu0/cpufreq/bios_limit 

To override that you need to type

# echo 1 > /sys/module/processor/parameters/ignore_ppc
# echo -n 2710000 >  /sys/devices/system/cpu/cpu1/cpufreq/scaling_max_freq
# cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_max_freq

However, in my case the bios_limit seems to be on regardless of whether I run on batteries, or AC. Overriding this limitation works as charm.

You may also need to update grub to force Ubuntu to ignore the bios limiting. This can be achieved by:

Opening the grub file:

sudo vim /etc/default/grub


+ GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_pstate=disable processor.ignore_ppc=1"

Update grub:

sudo update-grub


share|improve this answer
Linking to your source is good, but what if it goes offline some day? This answer would be much more useful to people having this problem in the future if you included how to test if this issue is affecting them and how to override the bios limit. – psusi Jun 4 '13 at 13:29
@psusi done, ths. – angainor Jun 4 '13 at 13:43

Don't know much about this side of things, but i think that cpufrequtils lets you do it by using

sudo apt-get install cpufrequtils
sudo cpufreq-set -r -g performance #-r for related (all) the cores
share|improve this answer
That does not help, unfortunately – angainor Jun 4 '13 at 10:38

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