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

Danny Mayer mayer at ntp.isc.org
Mon Jan 28 03:44:31 UTC 2008

David L. Mills wrote:
> Danny,
> It doesn't stop working; it just clamps whatever it gets to +-500 PPM as 
> appropriate. If the intrinsic error is greater than 500 PPM, the loop 
> will do what it can with the residual it can't correct showing as a 
> systematic time ofset.
> Dave

I didn't mean to suggest that ntpd stopped running. It was that the 
clock was drifting steadily off into the sunset. I realize that if the 
problem corrected itself ntpd would bring things back to normal.


> Danny Mayer wrote:
>> David L. Mills wrote:
>>> Danny,
>>> 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.
>>> Dave
>> Yes, I found this out when my laptop stopped disciplined the clock and 
>> was complaining about the frequency limits and I started digging into 
>> the code to figure out why.
>> Danny
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