clock problem

[M. Warner Losh]

In message: <20070508191617.GH838 at turion.vk2pj.dyndns.org>
            Peter Jeremy <peterjeremy at optushome.com.au> writes:
: There seems to be a bug in ntpd where the PLL can saturate at
: +/-500ppm and will not recover.  This problem seems too occur mostly
: where the reference servers have lots of jitter (ie a fairly congested
: link to them).

Yes.  This is a rather interesting misfeature of ntpd.  Its rails are
at +/- 500ppm, and when it hits the rail it assumes that things are
too bad to continue and it stops.

Most PC clocks have a frequency error on the order of 10-150ppm, so it
doesn't take a whole lot of jitter from a conjectsted remote network
to exceed the limits...

Warner