[ntp:questions] 10 identical PCs, but different clock drifts.

David J Taylor david-taylor at blueyonder.neither-this-bit.nor-this.co.uk
Mon Mar 2 17:33:57 UTC 2009

ryad.bek at gmail.com wrote:
> Hi everybody,
> I've bought 10 PCs with identical hardware (motherboard,...).
> The PCs are located in the same room and running identical
> configurations for 4 days now.
> They are synchronized using garmin 18 GPSes.
> I've just checked the NTP's loopstats file and it seems that all drift
> are different.
> Here are the reported drifts (4th column of loopstats file) :
> PC6=23,7
> As all hardware are the same and brand new, I was wondering if you
> find that normal or if there is a problem with my HW config?
> Regards
> Ryad

It's most likely that all the timing elements (quartz crystals) are not 
exactly on the same frequency.  The allowed tolerance on a consumer-cost 
crystal could be as bad as 0.01%, which is 100 parts per million (ppm). 
You are reporting values up to 24 ppm.  NTP allows up to 500 ppm.


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