[ntp:questions] Re: HowTo calibrate system clock frequency using NTP

Daniel Kabs daniel.kabs at gmx.de
Tue Jan 31 15:56:24 UTC 2006

Hello Professor Mills,

now I have a plan :-) Thank you.

I copied your valuable instructions into the NTP wiki at


I wonder why your procedures do not use "ntpdate". Is it because 
"ntpdate" is to be retired soon from your ntp distribution? Or will 
"ntpdate" fail to provide data as precise as ntpd? Indeed, I see a 
difference when I compare the drift file value against the offset 
measured by ntpdate:

A) I had ntp running for one day against a time server. The value in the 
drift file converged monotonously to -268.173. This gives a clock error 
of -23.17 s/day.

B) I configured ntp in order to serve the pseudo local clock. I 
periodically measured the time offset from a time synchronized PC using 
"ntpdate". A least-squares fit gives a slope of 23.87 s/day.

Any idea why is this?

Refactor, don't archive! - SamHasler - 28 Aug 2004 - twiki.org

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