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

ryad.bek at gmail.com ryad.bek at gmail.com
Mon Mar 2 22:27:50 UTC 2009


On Mar 2, 7:44 pm, "Richard B. Gilbert" <rgilber... at comcast.net>
wrote:
> ryad.... 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) :
>
> > PC1=15,6
> > PC2=1
> > PC3=-20,7
> > PC4=14,1
> > PC5=15,5
> > PC6=23,7
> > PC7=-7
> > PC8=3,1
> > PC9=3,6
> > PC10=4,3
>
> > 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
>
> Absolutely normal.
>
> The clock will {\italics usually} not gain or lose more than 43 seconds
> per day.  That's about the best you can hope for without paying for an
> add on clock OR using ntpd to discipline your clock.  The equivalent
> clock frequency error is +/- 500 Parts Per Million (PPM).
>
> Only random chance would give you two computers with the same clock
> drift rate.  Most will be somewhere between +/- 50 PPM.

For PC1, the drift rate has varied between 15.632 15.650 these two
last days

In deed, I use a home made 16-port GPS splitter to synchronize my PCs.
I'm very proud of it:)
I will try to release the design in the coming weeks/monthes.




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