[ntp:questions] two machines syncing to the same master - hardware issues?

unruh unruh at invalid.ca
Fri May 31 19:38:06 UTC 2013

On 2013-05-31, Steve Kostecke <kostecke at ntp.org> wrote:
> On 2013-05-31, matthew.garman at gmail.com <matthew.garman at gmail.com> wrote:
>> On Thursday, May 30, 2013 5:41:46 PM UTC-5, unruh wrote:
>>> You can expect offsets of the order of 10-20microseconds IF the ntp
>>> servers get their time from gps. If not, the servers themselves can
>>> be woggling all over the place.
> That's misleading.

Probably. What I was trying to emphasise is that in worrying about the
scatter of offsets on your machine, you have to wrry about the source as
well. One of my machines ( connected to a Garmin 18 gps) has a scatter
of offsets of about 100 usec. Clearly the Gamin has failed. (actually
they seem to produce crap, since both my Garmin 18s have failed over
about 3 years time). Clearly you can tell very little about your own
machine's timekeeping  if you use something like that machine as your source of
>> Is there any way to determine if the ntp servers are using GPS or not?
> Query them with ntpq. http://doc.ntp.org/4.2.4/ntpq.html
> But keep in mind that there other factors besides the time source at
> play here. 

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