# msr(4) - man - phpMan

[MSR(4)](https://www.chedong.com/phpMan.php/man/MSR/4/markdown)                                Linux Programmer's Manual                               [MSR(4)](https://www.chedong.com/phpMan.php/man/MSR/4/markdown)



## NAME
       msr - x86 CPU MSR access device

## DESCRIPTION
       _/dev/cpu/CPUNUM/msr_  provides  an  interface  to  read and write the model-specific registers
       (MSRs) of an x86 CPU.  _CPUNUM_ is the number of the CPU to access as listed in _/proc/cpuinfo_.

       The register access is done by opening the file and seeking to the MSR number  as  offset  in
       the  file,  and then reading or writing in chunks of 8 bytes.  An I/O transfer of more than 8
       bytes means multiple reads or writes of the same register.

       This file is protected so that it can be read and written only by the user _root_,  or  members
       of the group _root_.

## NOTES
       The  _msr_  driver  is not auto-loaded.  On modular kernels you might need to use the following
       command to load it explicitly before use:

           $ modprobe msr

## SEE ALSO
       Intel Corporation Intel 64 and IA-32 Architectures Software Developer's Manual Volume 3B  Ap‐
       pendix B, for an overview of the Intel CPU MSRs.

## COLOPHON
       This  page  is  part  of  release  5.10 of the Linux _man-pages_ project.  A description of the
       project, information about reporting bugs, and the latest version of this page, can be  found
       at <https://www.kernel.org/doc/man-pages/>.



Linux                                        2009-03-31                                       [MSR(4)](https://www.chedong.com/phpMan.php/man/MSR/4/markdown)