ntpq peers formatting needs floating point for time slots.

Gary E. Miller gem at rellim.com
Tue Feb 7 22:41:45 UTC 2017

Yo Achim!

On Tue, 07 Feb 2017 20:36:15 +0100
Achim Gratz <Stromeko at nexgo.de> wrote:

> Gary E. Miller writes:
> >> That slot should represent the number of useful bits.  
> >
> > Yup.  And in Selsky's case he really does have -30.  
> Nope.

I disagree.

> The resolution of the numbers is 1ns, the useful digits aka
> precision of the measurement doesn't extend that far down.  That -30
> would be equivalent to 931ps, 

-29 is 1.8 ns, and I claim that -30 (931 ns) is closer than -29.

> which is completely implausible.  I'll
> give you 30ns tops, that would be -25.  You supposedly can get down to
> about half that, but it needs another atomic clock as a reference.

In the past I would agree with you, but no longer.  

And either way, -25 or -30, that is way closer to the truth than the
current -20.  And since ntpd does not even use the precision it is
not worth arguing.

> http://www.allanstime.com/Publications/DWA/Science_Timekeeping/TheScienceOfTimekeeping.pdf
> https://ilrs.cddis.eosdis.nasa.gov/docs/timing/gpsrole.pdf
> The on-the-tin specification for GPS is 1µs, and that gives more or
> less exactly the -20 that the receiver reports, not so mysteriously
> after all.

That is a way old spec.  20 years old.  HP does not even exist anymore.

Look at something more modern.  Meinberg claims 50 ns for one product:


Parts like the ublox 8T claim better, < 20 ns accuracy:


So -30 can not be too far off.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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