linux-kernel - Re: AMD Quad Core clock problem?

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Message-ID: <e2e108260804130119r27a2ccb8sc7f03b43c6177d33@mail.gmail.com>
Date:	Sun, 13 Apr 2008 10:19:22 +0200
From:	"Bart Van Assche" <bart.vanassche@...il.com>
To:	"Marc Perkel" <mperkel@...oo.com>
Cc:	"Chris Snook" <csnook@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: AMD Quad Core clock problem?

On Sat, Apr 12, 2008 at 12:09 AM, Marc Perkel <mperkel@...oo.com> wrote:
>
>  Is it possible due to calibration that ntpd isn't able
>  to correct the problem? Is there a setting to make ntp
>  more agressive?

Clock crystals typically have an error between 20 and 200 ppm. ntpd
can correct clock crystal errors of maximum 500 ppm. If I remember
correctly the kernel limits frequency adjustments to 512 ppm. It's not
a good idea to try to change this limit -- large clock crystal errors
slow down convergence of ntpd's algorithms significantly.

Bart.
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