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.. SPDX-License-Identifier: GPL-2.0+
.. index::
single: msr (command)
msr command
===========
Synopsis
--------
::
msr read <op>
msr write <op> <hi> <lo>
Description
-----------
The msr command reads and writes machine-status registers (MSRs) on x86 CPUs.
The information is a 64-bit value split into two parts, <hi> for the top 32
bits and <lo> for the bottom 32 bits.
The operation <op> selects what information is read or written.
msr read
~~~~~~~~
This reads an MSR and displays the value obtained.
msr write
~~~~~~~~~
This writes a value to an MSR.
Configuration
-------------
The msr command is only available on x86.
Return value
------------
The return value $? is 0 (true).
Example
-------
This shows reading msr 0x194 which is MSR_FLEX_RATIO on Intel CPUs::
=> msr read 194
00000000 00011200 # Bits 16 (flex ratio enable) and 20 (lock) are set
This shows adjusting the energy-performance bias on an Intel CPU::
=> msr read 1b0
00000000 00000006 # 6 means 'normal'
=> msr write 1b0 0 f # change to power-save
=> msr read 1b0
00000000 0000000f
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