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

Richard B. Gilbert rgilbert88 at comcast.net
Mon Mar 2 18:44:22 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) :
> 
> 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.




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