[ntp:questions] ntp & system without a rtc

unruh unruh at invalid.ca
Wed May 15 17:47:06 UTC 2013

On 2013-05-14, David Woolley <david at ex.djwhome.demon.invalid> wrote:
> Richard B. Gilbert wrote:
>> NTPD is NOT designed for fast convergence.  From start up to get the 
>> minutes correct, NTPD will need about thirty minutes!  To get the best 
>> time you are going to get, you will need to wait for about ten hours!
> Convergence to within 128ms should take a lot less than that.  With 
> iburst, I believe it should be less than one minute.

Since ntpd steps ( changes the rate by an infinite slope) if the time is
out by 128 ms, yes, convergence IS faster than that. ( however it has to
make sure that the clock really is out by that much and that takes a few
cycles of clock querrying).

For a ms accuracy your could expect a couple of hours. for 10
microsecond, about 10 hr. 

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