# [ntp:questions] Any chance of getting bugs 2164 and 1577 moving?

Alby VA albyva at empire.org
Wed Mar 21 23:39:20 UTC 2012

```On Mar 21, 7:36 pm, unruh <un... at invalid.ca> wrote:
> On 2012-03-21, Alby VA <alb... at empire.org> wrote:
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> > On Mar 21, 3:55?pm, unruh <un... at invalid.ca> wrote:
> >> On 2012-03-21, David J Taylor <david-tay... at blueyonder.co.uk.invalid> wrote:
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> >> > "unruh" <un... at invalid.ca> wrote in message
> >> > []
> >> >> But -19 is about 2 microseconds if I understand it correctly. That means
> >> >> that the clocks are incapable of delivering more than about 2
> >> >> microseconds of accuracy. What is you ?that last decimal digit of
> >> >> accuracy in the offset is thus pure noise-- dominated by clock reading
> >> >> noise. Why is it important for you then?
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> >> > When I can see the decimal places, then I will know whether the precision
> >> > estimate is reasonable. ?Just getting values such as -1, 0, 1 microseconds
> >> > is insufficient to make that call.
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> >> And how will the extra decimals help? The -19 was determined by making
> >> successive calls to the clock and seeing how much it changed between
> >> successive readings. That gives a good estimate of how long it takes to
> >> make a call to the clock. Any precision in the answer beyond that is not
> >> accuracy. I could give you the time to 60000 decimal places, each one of
> >> the diffetent, but the last 5995 just being garbage (random numbers)
> >> Would that tell yo uanything?
> >> If for some reason you do not believe ntpd's estimation of your clock
> >> accuracy, develope a better algorithm for determining it. It is a bug is
> >> ntpd is reporting an accuracy much worse than it actually is.
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> >> Ie, you have no data to make that call even if you get more digits.
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> >> > David
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> > unruh:
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> >   My take is the precision output might say your device is -19 so you
> > know its
> > accuracy is around 2/microseconds. But the offset several decimal
> > places
> > allows you to see its ever changing accuracy within that 2/microsecond
> > band
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> But that is not accuracy. That is presumably (if that -19 is accurate
> and not a bug) is simply noise. If your measurement technique is only
> good to 2us, then any additional precision is just noise. It may be fun
> to see the noise, but not terribly useful. If it is not noise, then that
> -19 is wrong, and one has a bug in the determination of the accuracy of
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> > to a greater detail than just -1, 0, or 1 microseconds. I guess its
> > just a matter
> > of getting more granular details for cool MRTG charting. :)
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> It could well be that charting looks better without just bands on the
> page. But is it worth it if that detail is just junk? It certainly is
> not great art.

It there any good way to determine what is noise and what isn't?

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