[ntp:questions] Loop Frequency and Offset
mail at miguelgoncalves.com
Tue Sep 27 10:29:31 UTC 2011
On 27 September 2011 01:29, unruh <unruh at wormhole.physics.ubc.ca> wrote:
> Any(?) gps receiver which has PPS output does better than 1us. Any
> network does much worse than 1 us ( more like 10s of us to hundreds).
I might be wrong but checking for instance the Garmin 18 LVC specifications
(http://www8.garmin.com/products/gps18oem/spec.html) I do not see better
than 1 us accuracy.
> > I know... :-) My cable connection is really bad for NTP... I can't get
> > better than 3 us. That is why I have 2 stratum 1 GPS receivers onsite.
> You will NOT bet 3us from any network connection.
> Are you sure you are not confusing microseconds (us) with milliseconds
I don't mix ms and us... I wasn't BETTING on anything... :-) It was a typo
of course (errare humanum est).
> And even with a high accuracy timing receiver you will not get better
> than ab out 1us because of hardware interrupt latencies and variability,
> etc (and thermal wandering of your computer clock) unless you have some
> very specialised hardware.
1 us is OK for me.
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