[ntp:questions] systems won't synchronize no matter what

David L. Mills mills at udel.edu
Tue Nov 2 13:33:25 UTC 2010


Miroslav,

The extra complexity is not worth the benefit.

Dave

Miroslav Lichvar wrote:

>On Mon, Nov 01, 2010 at 02:49:57PM +0000, David L. Mills wrote:
>  
>
>>There is a very good reason. First, the kernel can an only be
>>switched between PLL and FLL mode discreetly, while the daemon has a
>>gradual transition between modes so that the poll interval can vary
>>seamlessly between 8 s and 36 hr. Second, the kernel PLL is most
>>useful to minimize sawtooth errors, and is no better than the daemon
>>loop to track incidental frequency noise. Seldom if ever is it
>>useful to switch to FLL mode at poll intervals less than 1024 s,
>>unless the incidental phase noise is less than a microsecond.
>>    
>>
>
>I know the kernel FLL is slightly different from the daemon FLL, but
>from the clknetsim tests it looked like FLL at 64s polling interval
>could be useful even with 100us phase noise.
>
>In any case, would it make sense to use the shorter kernel FLL when
>tinker allan is set to 8 or less? Similarly to the daemon loop, but
>only with one step.
>
>  
>




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