On Wed, Feb 18, 2015 at 10:00:08PM -0500, Paul wrote: > On Wed, Feb 18, 2015 at 8:53 PM, William Unruh <un...@invalid.ca> wrote: > > On 2015-02-19, Paul <tik-...@bodosom.net> wrote: > > > In the specific case of PPS I don't see any advantage. > > > > Well, no. Lichvar did some tests with PPS and found that chrony > > disciplined the clock much better than did ntpd (factors of over 10). I > > think that is a difference. > > > > Do you have a link to that? The graphs I saw were all for (simulated?) > clients. But it's been a while.
It could be this post http://lists.ntp.org/pipermail/questions/2010-March/026157.html My update to that after the years would be that 3x is not really the minimum difference. If the clock is stable enough, they can perform similarly. > A difference is not necessarily an advantage (I said advantage not > difference) but I would have assumed that < > https://github.com/mlichvar/chrony/blob/master/README> was correct which > says one microsecond* (I assume offset but it's unclear) but let's go with > 10x NTPd. On my machines NTPd offsets and jitter can be sub-microsecond. > So the target is O(10) nanoseconds? I don't think 10 nanoseconds is possible with 1us jitter and normal unstabilized clock. When using a PTP clock on PCIe as a reference it can get quite close though, see this graph from stats collected over a few hours: https://mlichvar.fedorapeople.org/chrony/refclock_phc0.png -- Miroslav Lichvar _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
