Hello!
I am trying to undervolt a sandy bridge i5 processor. I am running elementary OS loki, which is based on Ubuntu 16.04.
I am a bit confused about what steps are necessary to get undervolt working. I was able to install the intel-phc just fine with the "make dkms_mkdeb" command (running in the rev26 version folder) and with the grub trick that is posted in this thread. However, the following seems to indicate that voltages cannot be read properly:
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cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
31:0 25:0 20:0 16:0 12:0 8:0
Note that all voltages are "0".
1. Do I need to re-compile the kernel? The file you can get
here does mention in a special Ubuntu readme that a separate kernel is necessary.
On the other hand, there is another release
here which mentions: "Using this package you can build a patched module outside the kernel tree.
(You do not need to patch your Kernel anymore)" -- regarding a special "offtree" version.
Are these two statements contradictory? Does in not apply to Ubuntu?
2. acpi_cpufreq will not show up in "lsmod", but it will show up in "ls /sys/module". Even after installation of intel-phc and after the grub settings change in this thread, it will show up. Is that expected behavior? Is there a way to test which CPU control method is active?
All help is much appreciated.
EDIT: I forgot to add, I am running on the 4.13 kernel. I have also tried the more modern version of undervolting which uses msr-tools and rdmsr/wrmsr. I have had no luck with them, as rdmsr always gives me an error that the commonly used register for undervolting is not readable.
EDIT 2: "dmesg | grep phc" gives the following:
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[ 3.426785] phc_intel: loading out-of-tree module taints kernel.
[ 3.426819] phc_intel: module verification failed: signature and/or required key missing - tainting kernel