[ntp:questions] best gps receiver for time synchronization

David J Taylor david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Wed May 13 05:36:38 UTC 2009

Unruh wrote:
> OK, I keep forgetting. What accuracy can the clock be read on windows?
> is there an interpolation routine in the kernel so the clock can be
> read
> to usec accuracy?
> I would thin k you could set up and interrupt routine to read and
> record
> the clock time when the interrupt occurs.


- with operating system calls, the main clock can be read with a precision 
of 1 millisecond (although the ticks may be only 15 milliseconds).  There 
are higher resolution counters which can also be read.

- yes, for NTP's internal use there is an interpolation routine, recently 
updated by Dave Hart.

- yes, Dave Hart has a modified device driver which records the time in 
kernel mode, rather than the more usual user-mode timestamping.  On my 
main stratum-1 PC, this reduced the jitter reported by NTP (and averaged) 
from around 5 microseconds to around 2.2 microseconds.


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