Warning! This program is untested (apart from by myself) and it may damage your hardware! Use at your own risk.
undervolt is a program for undervolting Intel CPUs under Linux. It works in a similar manner to the Windows program ThrottleStop (i.e, MSR 0x150). You can apply a fixed voltage offset to one of 5 voltage planes, and override your systems temperature target (CPU will throttle when this temperature is reached).
For more information, read here.
From PyPi:
$ pip install undervolt
From source:
$ git clone https://github.com/georgewhewell/undervolt.git
Read current offsets:
$ undervolt --read temperature target: -0 (100C) core: 0.0 mV gpu: -19.53 mV cache: -30.27 mV uncore: -29.3 mV analogio: -70.31 mV
Apply -100mV offset to CPU Core and Cache:
$ undervolt --core -100 --cache -100
Apply -75mV offset to GPU, -100mV to all other planes:
$ undervolt --gpu -75 --core -100 --cache -100 --uncore -100 --analogio -100
Set temperature target to 97C:
$ undervolt --temp 97
Generated the command to run to recreate your Throttlestop settings:
$ undervolt --throttlestop ThrottleStop.ini --tsindex 3 undervolt --core -100.5859375 $ undervolt --throttlestop ThrottleStop.ini undervolt --core -125.0 --gpu -125.0 --cache -125.0
$ undervolt -h usage: undervolt.py [-h] [-v] [-f] [-r] [-t TEMP] [--temp-ac TEMP_AC] [--temp-bat TEMP_BAT] [--throttlestop THROTTLESTOP] [--tsindex TSINDEX] [--core CORE] [--gpu GPU] [--cache CACHE] [--uncore UNCORE] [--analogio ANALOGIO] optional arguments: -h, --help show this help message and exit -v, --verbose print debug info -f, --force allow setting positive offsets -r, --read read existing values -t TEMP, --temp TEMP set temperature target --temp-ac TEMP_AC set temperature target on AC power --temp-bat TEMP_BAT set temperature target on battery power --throttlestop THROTTLESTOP extract values from ThrottleStop --tsindex TSINDEX ThrottleStop profile index --core CORE offset (mV) --gpu GPU offset (mV) --cache CACHE offset (mV) --uncore UNCORE offset (mV) --analogio ANALOGIO offset (mV)
First, create a unit file /etc/systemd/system/undervolt.service
with
following contents, replacing the arguments with your own offsets:
[Unit] Description=undervolt [Service] Type=oneshot # If you have installed undervolt globally (via sudo pip install): ExecStart=undervolt -v --core -150 --cache -150 --gpu -100 # If you want to run from source: # ExecStart=/path/to/undervolt.py -v --core -150 --cache -150 --gpu -100
Check that your script works:
$ systemctl start undervolt
Then create a timer /etc/systemd/system/undervolt.timer
to trigger the task periodically:
[Unit] Description=Apply undervolt settings [Timer] Unit=undervolt.service # Wait 2 minutes after boot before first applying OnBootSec=2min # Run every 30 seconds OnUnitActiveSec=30 [Install] WantedBy=multi-user.target
Now enable and start the timer:
$ systemctl enable undervolt.timer $ systemctl start undervolt.timer
By including the OnBootSec command, settings will not be immediately applied. If you have set overly-aggressive offsets, you will have a short period to disable the timer before it crashes your system:
$ systemctl stop undervolt.timer
Now you can edit your undervolt.service
before re-starting the timer.
Undervolting should work on any CPU later than Haswell.
System | CPU | Working? |
---|---|---|
Lenovo Yoga 920 | i7-8550U | Yes |
Lenovo X1 Gen 5 | i7-7500U | Yes |
Lenovo X1 Yoga Gen 2 | i7-7600U | Yes |
Lenovo Thinkpad T470p | i7-7700HQ | Yes |
Dell Latitude 7390 | i7-8650U | Yes |
Dell XPS 13 9343 | i5-5200U | Yes |
Dell XPS 15 9550 | i7-6700HQ | Yes |
Dell XPS 15 9560 | i7-7700HQ | Yes |
Dell XPS 15 9570 | i9-8950HK | Yes |
Dell XPS 15 9575 | i7-8705G | Yes |
HP Spectre X360 | i7-8809G | Yes |
HP Zbook Studio G5 | i7-8750H | Yes |
MacBook Air Mid 2013 | i5-4250U | Yes |
Acer Nitro 5 | i5-7300HQ | Yes |
- Core or Cache offsets have no effect. It is not possible to set different offsets for CPU Core and Cache. The CPU will take the smaller of the two offsets, and apply that to both CPU and Cache. A warning message will be displayed if you attempt to set different offsets.
OSError: [Errno 1] Operation not permitted
First try running withsudo
. If the error persists, your system is probably booted in Secure Boot mode. In this case, the Linux kernel will prevent userspace programs (even as root) from writing to the CPU's model-specific registers. Disable UEFI Secure Boot in your system's BIOS and the error should go away.
This project is a trivial wrapper around the work of others from the following resources:
- https://github.com/mihic/linux-intel-undervolt
- http://forum.notebookreview.com/threads/undervolting-e-g-skylake-in-linux.807953
- https://forums.anandtech.com/threads/what-controls-turbo-core-in-xeons.2496647
Many thanks to all who contributed.