On 2015-02-12, Paul <tik-...@bodosom.net> wrote: > On Thu, Feb 12, 2015 at 12:00 PM, William Unruh <un...@invalid.ca> wrote: > >> This means that if you are using say a PPS source, which gives >> microsecond long term offset, it can take many hours to get there >> > > This has been asserted and corrected before -- as in years ago*. A > properly configured Linux system with a PPS reference will achieve > best-possible short-term performance between 300-1200 seconds**. This > should be microsecond offset and jitter. An optimal drift estimate may > take longer. > > *It wouldn't suprise me if it was Mills correcting you. > **Depending on initial conditions.
It was based on measurements I made with ntpd See for example www.theory.physics.ubc.ca/chrony/chrony.html See the section toward the end Chrony vs NTP comparison for the rate convergence and the offset convergence of ntpd vs chrony. The exponential decay of the offset and of the rate had a time scale of about .05 day or about 1 hour. Ie, eac hour the offset would drop in half. I one goes from 1 ms to 1 us that is 10 decay times or about half a day. Note that the how long it takes to converge depends on the error that needs correcting. Those are based on experiments, not theory. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
