[ntp:questions] NTP vs chrony comparison (Was: oscillations in ntp clock synchronization)

David L. Mills mills at udel.edu
Mon Jan 28 16:33:26 UTC 2008


Maarten,

Maybe I didn't make myself clear. The case in question is when the 
intrinsic frequency error of the computer clock is greater than 500 PPM, 
in which case the discipline loop cannot compensate for the error. The 
result is a systematic time offset error that cannot be driven to zero. 
This has nothing to do with the initial offset as you suggest.

Dave

Maarten Wiltink wrote:
> "Unruh" <unruh-spam at physics.ubc.ca> wrote in message
> news:hr3nj.30520$yQ1.25135 at edtnps89...
> 
>>>David L. Mills wrote:
> 
> 
>>>>Unless the computer clock intrinsic frequency error is huge, the
>>>>only time the 500-PPM kicks in is with a 100-ms step transient and
>>>>poll interval 16 s. The loop still works if it hits the stops; it
>>>>just can't drive the offset to zero.
> 
> [...]
> 
>>Why can't it drive the offset to zero? 100ms should take about 5 min(if
>>it were always 500 but the loop would make it take longer)
> 
> 
> That would presumably be in the case of 'huge intrinsic frequency error'.
> 
> Groetjes,
> Maarten Wiltink
> 
> 




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