[ntp:questions] NTPD can take 10 hours to achieve stability

David J Taylor david-taylor at blueyonder.co.uk.invalid
Mon Apr 18 05:04:19 UTC 2011

"C BlacK" <rblak at non.net> wrote in message 
news:o-adnVWgbZB3NTbQnZ2dnUVZ_oCdnZ2d at supernews.com...
> Why would it take ntpd ten hours to achieve its accuracy?  Can this be 
> explained in laymans terms and
> mathematically

What accuracy do /you/ want?  For best accuracy which NTP can achieve, in 
the order of microseconds or better, your PC may need to be in a 
temperature controlled environment - how long would it then take to 
stabilise its own temperature?  Compare people using the best frequency 
sources, who may need to leave them for days to achieve their best 
accuracy.  On the other hand, if all you need is, say, 20ms (the clock 
interrupt period on many Windows PCs, so as accurate as a typical program 
could measure) then NTP might be that accurate just as soon as you've 
logged in.

The time taken to stabilise will typically depend on what accuracy /you/ 
want to achieve, so "ten hours" alone is meaningless out of context.


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