[ntp:questions] Speed of ntp convergence

David J Taylor david-taylor at blueyonder.neither-this-part.nor-this-bit.co.uk
Thu Nov 6 06:57:20 UTC 2008

Nicola Berndt wrote:
> I just recently tested my ntp-(pps-)machine in a large open hall and
> found it to be unable to settle down even after a day! It looks like
> the temperature changes in this open hall environment make the machine
> jitter with values between -200 and 200 ms regularly and
> unpredictable. Whenever I checked it, values were wildly varying
> inbetween those.. The same machine was able to at least settle down
> after an hour or so in a heated inside environment. I slowly come to
> believe that ntp simply lacks switches for adjusting how drastically
> the slewing is done in case the environmental temperature is varying
> drastically as well.
> Best regards,
> ../nico berndt


>From what you report, I would suggest that something is very broken.  I 
have a PC (FreeBSD, NTP, PPS GPS source) running in a domestic environment 
where, at the moment the central heating comes on at 0600.  Here is the 
reported offset:


Switching the room heating on causes 10usec offset, not 200msec.

The other Windows PCs synced from that PC are generally within 10msec:



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