Ubuntu – Cannot change Intel turbo boost (/sys/devices/system/cpu/intel_pstate/no_turbo/ not accessible)

administratorcpueditingintelsudo

Trying to follow this answer under Disabling Intel Turbo Boost in ubuntu:

In order to see the driver:

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_driver
intel_pstate
intel_pstate
intel_pstate
intel_pstate

Then, to inquire as to the turbo enabled or disabled status:

cat /sys/devices/system/cpu/intel_pstate/no_turbo
1

That means it's on.

To disable it, I get "Operation not permitted":

echo "0" | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
[sudo] password for cipeos: 
0
tee: /sys/devices/system/cpu/intel_pstate/no_turbo: Operation not permitted

Trying a suggestion in a comment under the answer (sudo echo "0" | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo) I get the same thing. Even sudo su before that gives the same.

Trying to find manually the file:

sudo gedit /sys/devices/system/cpu/intel_pstate/no_turbo

It has just one line:

1

When I try to change it to 0 and save it it says: "Could not save the file “/sys/devices/system/cpu/intel_pstate/no_turbo”." and "You do not have the permissions necessary to save the file. Please check that you typed the location correctly and try again."

enter image description here

Best Answer

  • The turbo enabled or disabled flag can be misleading. Excerpt from Documentation/cpu-freq/intel-pstate.txtin the source tree:

    Sysfs will show :
            max_perf_pct:100, which corresponds to 1 core ratio
            min_perf_pct:24, max_efficiency_ratio / max 1 Core ratio
            no_turbo:0, turbo is not disabled
            num_pstates:26 = (max 1 Core ratio - Max Efficiency Ratio + 1)
            turbo_pct:39 = (max 1 core ratio - max non turbo ratio) / num_pstates
    

    So, in this case the "1" means turbo is disabled. For most computers, turbo can be disabled in the BIOS, in which case one can not override the indicator flag in Sysfs. Example 1 (turbo is disabled in the BIOS):

    $ echo 0 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
    0
    tee: /sys/devices/system/cpu/intel_pstate/no_turbo: Operation not permitted
    

    Example 2 (turbo is enabled in the BIOS):

    $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
    1
    $ echo 0 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
    0
    $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
    0
    
  • Related Question