Re: TS-7200: time sync issues

[Simon Burge <simonb%NetBSD.org@localhost>]

Ken Hornstein wrote:

> >What you are describing here is a frequency error.  ntpd adjusts both
> >the phase of the clock, and its frequency.  Usually the initial
> >inspection period is sufficient to get the initial estimate to within
> >a tens or hundreds of microseconds, and the frequency to with a ppm or
> >two (later it gets much better).  This means in the 1000s that your
> >logs showed the clock should have drifted on the order of maybe 1ms.
> >Instead, it drifted by 200ms, 100x too much.
> 
> Sigh.  I don't know how to explain this any clearer.
> 
> RIGHT AFTER the clock is stepped, ntpd reports the time being off ... by
> a lot (that's the 100-900ms I was talking about).  During the 15 minutes
> or so that ntpd takes to reset itself, the this clock offset changes very
> little.  I don't understand how that can be a frequency error.  If it was
> a frequency error, it would never get in sync, but it does.
> 
> Am I just not explaining this well?

I'd guess some catastrophic arithmetic error in the time counter code
(see other examples of wrong mask earlier in this thread) or clock
interrupts being blocked for too long.

With ntpd disabled, what does something like:

        while true; do
           ntpdate -q <some-ntp-server(s)> | grep adjust
           sleep 1
        done

show?  Any obvious drift.  Maybe adjust the "sleep 1" if it takes longer
to see the problem.

Cheers,
Simon.