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#1 2016-09-21 10:43:11

buntolo
Member
Registered: 2011-10-11
Posts: 202

undevolt intel CPU

I want to regulate CPU voltages and I can't find any way do do so on Linux (on Windows I use ThrottleStop).

The only thing I've found is intel-phc: https://wiki.archlinux.org/index.php/PHC

But it works only with acpi-cpufreq and not intel_pstate, since Linux 4.7 came out intel_psate performances degraded and the new schedutils is doing greate.

1) How do I use phc?
2) Is the new scheduitl governor used with acpi-cpufreq?
3) If 2) is true, how do I use acpi-cpufreq?

I've done this but it's not working:

/etc/modules-load.d/acpi-cpufreq

# Load acpi-cpufreq at boot
acpi-cpufreq

But it doesn't load acpi-cpufreq at boot:

% lsmod | grep -i acpi                              :(
1 a

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#2 2016-09-21 12:54:28

pedrogabriel
Member
From: Brazil
Registered: 2014-08-17
Posts: 30

Re: undevolt intel CPU

The pstate power scaling driver is used automatically for modern Intel CPUs instead of the other drivers below. This driver takes priority over other drivers and is built-in as opposed to being a module. Add

 intel_pstate=disable 

to your kernel line to disable it and use acpi instead.

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#3 2016-09-21 13:00:28

buntolo
Member
Registered: 2011-10-11
Posts: 202

Re: undevolt intel CPU

I already have intel_pstate=disable in kernel line and phc-intel is being loaded:

% cpupower frequency-info
analisi della CPU 0:
  driver: phc-intel

I can't disable this driver:

% cat /proc/cmdline
\vmlinuz-linux ro root=UUID=5e5ecd52-77a7-42c7-a997-0aef9d5cd654 ro quiet splash intel_pstate=disable phc_intel=disable phc-intel=disable initrd=\initramfs-linux.img

I'm following this guide: https://wiki.archlinux.org/index.php/PHC

'phc-intel setup' seems to be non-existent, so I've installed dkms-phc-intel.

wiki says it should load acpi-cpufreq module but it's not, so I'm stuck, running '$ dmesg | grep acpi-cpufreq' shows nothing (returns 1 in zsh)

Last edited by buntolo (2016-09-21 13:20:23)

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#4 2016-09-21 13:05:02

pedrogabriel
Member
From: Brazil
Registered: 2014-08-17
Posts: 30

Re: undevolt intel CPU

I think it means you are actually using phc, and if I understanded right, it's what you want. So, what's the problem?

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#5 2016-09-21 13:21:39

buntolo
Member
Registered: 2011-10-11
Posts: 202

Re: undevolt intel CPU

pedrogabriel wrote:

I think it means you are actually using phc, and if I understanded right, it's what you want. So, what's the problem?

According to that guide, acpi-cpufreq should be loaded but it's not, the mprime script doesn't work.

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#6 2016-09-21 18:34:03

ooo
Member
Registered: 2013-04-10
Posts: 1,637

Re: undevolt intel CPU

See the 'Troubleshooting' part in PHC arch wiki page regarding module loading, and everything else.

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