[Bug 43281] Core Duo / Pentium M high pitched buzzing noise: CONFIG_HZ workaround

[John Dong]

Public bug reported:

Affects: linux-source-2.6.15 (Ubuntu)
       Severity: Normal
       Priority: (none set)
         Status: Unconfirmed


Description:
Almost all core duo laptops and even some Pentium M thinkpads will
produce a high-pitched buzzing/whirring noise when one or more CPU's
enter the C3 or C4 states. So far, the workaround has been to disable
C3/C4 using the max_cstate sysfs parameter, but that results in greatly
diminished battery life, especially on the Cores, whose C3/C4 states are
amazingly good at conserving battery power.

Another workaround that has a very high rate of success is reducing
CONFIG_HZ from 1000 (desktop default) to 100 (what our server kernel
uses). It yields virtually no change in desktop performance, and often
eliminates the noise while allowing both cores to reach the C3/C4
states.

Unfortunately, our only 100Hz kernel (server) does not come with
restricted modules.

If we can get a separate 686-100hz kernel (the Intel Pentium M / Core
lines are the only ones with this problem, to my knowledge) that comes
with restricted modules, that'd make lots of Thinkpad and Core Duo
owners very happy :)

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Core Duo / Pentium M high pitched buzzing noise: CONFIG_HZ workaround
https://launchpad.net/bugs/43281