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

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Mon Mar 2 20:17:43 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?

Those numbers are actually very good!

Anything below 100 is a good crystal, and NTP itself was modified a long 
time ago to allow up to 500.

It is only the second-order variations that matter, i.e. how 
temperature-stable are those drift rates?

- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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