[ntp:questions] Slow convergence of NTP with GPS/PPS

Hal Murray hal-usenet at ip-64-139-1-69.sjc.megapath.net
Thu Oct 2 18:55:33 UTC 2008

>The driftfile also sometimes seems to do more harm than good - especially
>after a reboot.

How stable is your temperature?  Are you rebooting a happy system?
(If so why?)  Or are you powering up a system that has been off
for the night?

If your drift file is off, I would expect things like this:
>  Also, even if we set the time pretty much perfect (within 5ms offset), ntpd
> appears to first *increase* the offset to well out of our spec, then correct
> through zero offset - overshooting the other way (again well out of our
> spec) and then typically crawls back in after which it is stable - and
> ultimately wonderfully accurate and stable.

If your temperature is unstable, I think you are going to have troubles
getting started cleanly.  (Note that CPU activity may influence your

Since you seem willing to hack the sources, I would suggest finding
the code where it does the once-only big step and making that do
small steps too, even if it wouldn't normally do a step.

That may not work, but it's what I would try first.

These are my opinions, not necessarily my employer's.  I hate spam.

More information about the questions mailing list