[ntp:questions] Re: clock resolutions for different OS

David L. Mills mills at udel.edu
Tue Aug 19 22:19:48 UTC 2003


Drk,

The resolution is defined with respect to the raw clock reading function
only and has nothing to do with the tick value. Values in the low
nanoseconds are common with modern processors. The precision displayed
in the NTP billboards is defined as the minimum time to read the system
clock, including the overhead due to kernel interface, etc., and ranges
from 40 us in older processors to 0.4 us in a Blade 1000. While the tick
value constrains the epoches for timer interrupts, it plays no part in
the precision of the NTP measured clock offset and network delay.

Dave

Drk Ryan wrote:
> 
> Since operating systems such as Linux, Solaris, certain versions of
> Unix, and WinNT all run at 100Hz clock resolution how is it that their
> timimg suppport varies: FreeBSD handles nanoseconds, Linux handles
> microseconds and WinNT only ~10 milliseconds?
> 
> As 1/100Hz = 10ms should they all not return a resolution of 10ms?



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