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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 
2000000

# 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 
2000000

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 
800000

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

# echo 2200000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 
# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq 
2000000

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?

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2 Answers 2

up vote 13 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 
2000000

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
2710000

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.

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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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