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CPU MSR register "tweak" module?

From: Nils Faerber
Subject: CPU MSR register "tweak" module?
Date: Fri, 28 Sep 2012 14:27:58 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120827 Thunderbird/15.0

Recently I purchased an AMD E-450 based netbook - my first AMD CPU for a
long time. As expected Grub works perfectly on it - as does the Debian
Linux I did install.

Many AMD CPUs, and some Intel CPUs maybe too, can be tweaked for way
lower power consumption by modifying the CPU MSR registers to lower the
core voltage and eventually also the frequency (per P-state).

The drawback of this is that the new values are lost upon reboot or
suspend-to-disk. And additionally some of the Linux kernel drivers that
get loaded or re-initialised during boot/resume pick up those values
from those registers before user-space can re-setup them.

So I was wondering if there is a possibility to configure Grub in a way
that it will set-up specific registers with specific values. Ideally
using the Grub config file... a small table with register/value pairs
would be enough and they can just be written to the MSR registers
without additional magic, so such a function should be pretty easy to
implement - if it does not exist yet.

I did search through the docs and also had a brief look at the Grub
source but could not find something like that.


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