Re: [PATCH] Option to synchronize P-states for AMD family 0xf

Joerg Roedel
2009-09-30T10:00:57Z

On Tue, Sep 29, 2009 at 04:23:55PM -0500, Mark Langsdorf wrote:

> AMD Family 0xf processors (Athlon 64s and Opterons) do not
> have P-State or C-State invariant TSCs. Instead, the TSC
> increments at the current processor frequency, which makes
> it unstable and unreliable if cpufreq is enabled.
>
> This patch introduces a new command parameter for the
> PowerNow! driver called "tscsync". When tscsync is
> set to 1, the driver forces all processors in the system
> to change frequency as the same time to the same frequency.
> This unified change means that all the TSCs in the system
> increment at the same rate.

Cool feature. Does Linux consider the TSC as stable on these machines
even after a longer uptime (say after a week)?

Joerg