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Message-ID: <e2e108260804162317s5162a6cds151bba6abf988921@mail.gmail.com> Date: Thu, 17 Apr 2008 08:17:31 +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 Wed, Apr 16, 2008 at 11:44 PM, Marc Perkel <mperkel@...oo.com> wrote: > --- Bart Van Assche <bart.vanassche@...il.com> wrote: > > It's better to correct the clock frequency once with > > the tickadj or adjtimex, so you don't have to add > > ntpdate to cron and you can still run ntpd. > > > > Bart. > > ok - thanks. How do I do that? You can do that as follows: * First of all, make sure that adjtimex is installed. Some distro's include this command in util-linux. * Query the current tick value via adjtimex -p | grep tick. E.g. with HZ = 100, tick == 10000. * Multiply the tick value with the relative clock error: when e.g. 3s are lost every hour, the correct tick value is 10000 * (1 + 3/3600) = 10008. * Pass this new tick value to the kernel via adjtimex -t 10008. * Stop and restart ntpd such that it forgets any previous frequency estimates. * Keep an eye on the output of adjtimex -p|grep frequency to see whether the frequency estimate converges (should be stable within 10 ppm after an hour. See also man adjtimex for the units of this value). Bart. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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