[ntp:questions] NTP server with Garmin GPS 18 LVC

Adrian P ntp at pascalau.ro
Fri Dec 20 21:59:51 UTC 2013


On 19 December 2013 01:16, unruh <unruh at invalid.ca> wrote:
> So it repeats approx every 1.5  hours, quite regularly (slightly longer
> period at night than during the day). Are you doing
> something on the machine every two hours? 9 minutes is a long time (
> over 30 time periods) so disk activity or other interrupt delays does
> not seem a reasonable explanation. I really do not have any idea why
> there would be this extremely regular long term delay

Nope, this is a fresh FreeBSD 9.2 installation. Just the base system
and the kernel were installed. I also compiled a new kernel with PPS
support. Only ntpd is running, and of course sshd for remote
connection.

In the end what is this clock offset? I suppose it is the difference
between my laptop's internal clock and the precise timing provided by
the GPS's PPS signal, right? When the laptop's internal clock remains
behind, I have a negative clock offset, and when the laptop's internal
clock rushes ahead I have a positive clock offset.... NTP will always
tries to align the internal clock of the laptop with the precise
timing received from the GPS's PPS signal.

Just wondering, could it be that the heating of the laptop causes
these spikes? The laptop heats itself, then the fans start working for
a while, until the temperature goes down. Then the laptop starts to
heat again, and so on...


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