[ntp:questions] how do I lock in average frequency correction

David Woolley david at ex.djwhome.demon.invalid
Sun Feb 12 10:53:07 UTC 2012

Ron Frazier (NTP) wrote:
> It is my understanding that NTP is continuously making small changes to 
> the software clock to keep the timing accurate while the os is running.  
> 95% of the time, my computers are doing the same thing and 95% of the 
> time, I'm doing the same thing with the computers.  Therefore, over a 
> long time interval, the interrupt usage should be similar, and over a 
> long time interval, the correct clock frequency to maintain accuracy 
> should be similar.

Although interrupt related issues can cause temporary changes in 
measured offset, which will self correct, the main issue is temperature 
changes, changing the actual clock frequency and also power management 
doing that.  If you can address temperature changes by other means 
(ovened crystal, etc.) and can avoid power management, you should not 
need to make step corrections, and, on Linux, you can use ntptime to 
tune the kernel time discipline parameters to find tune a fixed 
frequency correction.

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