[ntp:questions] Allan deviation survey

David L. Mills mills at udel.edu
Tue Sep 14 19:17:04 UTC 2010


Miroslav,

Better recalibrate your slide rule. On a 2.8 GHz dual-core Pentium 
running OpenSolaris 10, the measured precision is -21, which works out 
to 470 ns. You claim ten times faster. What snake oil are you using for 
your processor? To check, try running the jitter.c program in the 
distribution.

Dave

Miroslav Lichvar wrote:

>On Tue, Sep 14, 2010 at 02:45:01AM +0000, David L. Mills wrote:
>  
>
>>Don't get fooled by the MINSTEP. Precision is defined by the time to
>>read the system clock at the user interface and I have never seen
>>anything less than 500 ns for that, more typically 1000 ns.
>>    
>>
>
>This is what ntpd prints here (patched to use smaller MINSTEP):
>ntpd[9357]: proto: precision = 0.086 usec
>
>I've seen values as low as 40 ns. The system has to use TSC as
>clocksource though.
>
>  
>




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