ntpq peers formatting needs floating point for time slots.

[Gary E. Miller]

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:

https://www.meinbergglobal.com/english/products/pci-express-gps-clock.htm

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

https://www.u-blox.com/sites/default/files/products/documents/NEO-LEA-M8T-FW3_ProductSummary_%28UBX-16000801%29.pdf

So -30 can not be too far off.

RGDS
GARY
---------------------------------------------------------------------------
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
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 455 bytes
Desc: OpenPGP digital signature
URL: <https://lists.ntpsec.org/pipermail/devel/attachments/20170207/1136478e/attachment.bin>