How to change CPU scaling driver to intel_pstate

I have an iMac with an Intel(R) Core(TM) i7 CPU 870 @ 2.93GHz (1 physical, 4 cores, 8 threads)

I am on Ubuntu 18.04.3 LTS

I was trying miscellaneous stuff (most of which I don't even remember) in an effort to change the CPU frequency because it was always fixed to 1.2GHz (minimum).

Currently the acpi-cpufreq driver is used:

$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_driver
acpi-cpufreq
acpi-cpufreq
acpi-cpufreq
acpi-cpufreq
acpi-cpufreq
acpi-cpufreq
acpi-cpufreq
acpi-cpufreq

and I want to switch back to intel_pstate but I don't know how to achieve this.

When trying to switch to acpi-cpufreq I added the kernel parameter intel_pstate=disable in my /etc/default/grub. I removed it and I did execute sudo update-grub but after reboot I still get that acpi-cpufreq is the scaling driver.

Any hints?

1 Answer

GENERAL ANSWER:

Open terminal and type:
sudo gedit /etc/default/grub
Then find line:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
And change it to:
GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=enable quiet splash"
Save file and run following command:
sudo update-grub
Restart system and check is it enabled by:
sys/devices/system/cpu/cpu*/cpufreq/scaling_driver

ANSWER FOR INTEL PROCCESORS BEFORE 2nd GEN:

I am sorry but you can not use intel_pstate on your proccesor. It is only compactiable with proccesors from Sandy Bridge(2nd) generation up. You can only use old CPUfreq with Intel i7 870
EXTRA INFO: