Installing phc-linux undervolting module on Debian Jessie

First thing is to download Debian Jessie netinst image from mirror:

wget http://cdimage.debian.org/debian-cd/8.1.0/i386/iso-cd/debian-8.1.0-i386-netinst.iso

After standard Debian installation procedure you can download latest linux-phc from their forum:

wget http://linux-phc.org/forum/download/file.php?id=166 -O phc-intel-pack-rev17.tar.bz2

Unpack the package and enter directory:

tar xvfj phc-intel-pack-rev17.tar.bz2
cd phc-intel-pack-rev17/

Please read README.1st before continuing.

Install necessary packages for building kernel module:

apt-get install build-essential

Check which kernel version you are using and install appropriate headers:

uname -a
apt-get install linux-headers-3.16.0-4-686-pae

Since we will build .dep package you will also need to install:

apt-get install dkms debhelper

Make and install package:

make dkms_mkdeb
dpkg -i phc-intel-dkms_0.3.2_all.deb

Remove acpi_cpufreq module and load phc_intel for testing

rmmod acpi_cpufreq
modprobe phc_intel

Check if you see PHC controls for your CPU:

cat /sys/devices/system/cpu/cpu*/cpufreq/phc_vids
 34 21 11
 34 21 11

Values that I have tested and found working on my laptop are “19 0 0” and I will put them in /etc/rc.local file to be loaded as soon as system boots:

echo "19 0 0" > /sys/devices/system/cpu/cpu0/cpufreq/phc_vids
echo "19 0 0" > /sys/devices/system/cpu/cpu1/cpufreq/phc_vids

Now your system should have proper values set on each reboot.

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