Undervolting CPU - ArchWiki

# Undervolting CPU

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Related articles

- PHC
- CPU frequency scaling
- Improving performance
- Benchmarking
- Fan speed control

Undervolting is a process where voltage to CPU is reduced in order to reduce its energy consumption and heat without affecting performance. Note that most desktop motherboards allow tweaking CPU voltage settings in BIOS as well.

Warning: Misconfiguration of CPU voltage settings might result in permanently damaged hardware. You have been warned!

This article or section needs expansion.

Reason: Needs to be expanded. It could be that PHC needs to be merged here as well. (Discuss in Talk:Undervolting CPU#)

## Overview

- PHC - a tool to undervolt some old generation Intel and AMD processors. Not compatible with `intel_pstate` CPU frequency driver.
- #intel-undervolt - a tool for undervolting Haswell and newer Intel CPU using MSR. Compatible with `intel_pstate`.
- #amdctl - a tool for undervolting K10 and newer AMD CPUs.
- K10ctl - overclock and undervolt an AMD K10 processor (e.g. Phenom, Phenom II) by changing its P-States.

## Tools

### intel-undervolt

Intel-undervolt is a tool based on this article for undervolting Haswell and newer Intel CPUs using MSR and MCHBAR registers. In addition, it also allows to change power and temperature limits.

#### Installation

The tool can be installed as intel-undervoltAUR.

#### Configuration and usage

The following command prints in use voltage settings:

    # intel-undervolt read

Now edit the configuration file `/etc/intel-undervolt.conf`. Example config with undervolted CPU Cache by -100mV:

Note: Looks like 'CPU' and 'GPU' values does not have any effect (at least on ASUS Zenbook UX430UQ laptop).

    /etc/intel-undervolt.conf

    ...
    undervolt 0 'CPU' 0
    undervolt 1 'GPU' 0
    undervolt 2 'CPU Cache' -100
    undervolt 3 'System Agent' 0
    undervolt 4 'Analog I/O' 0
    ...

Once you saved configuration file - test it:

    # intel-undervolt apply

It will print Success if settings were applied. You can double check in use configuration using the following command:

    # intel-undervolt read

Once you find stable configuration, you can also enable `intel-undervolt.service` to make changes persistent.

### amdctl

amdctl is a tool for undervolting K10 and newer AMD CPUs.

#### Installation

The tool can be installed as amdctl-gitAUR.

Categories:

- CPU
- Power management

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