[ntp:questions] Why is my precision=-15? I'm using a nano kernel.

Chuck Swiger cswiger at mac.com
Tue Jan 15 19:05:41 UTC 2013


On Jan 15, 2013, at 10:18 AM, Edward T. Mischanko wrote:
> It means that successive calls to the gettimeofday function return with
> a difference that is not less than 2^-15 sec. 
> Thanks for the reply and the information.  Is -15 good, bad, or average?

Out of ~100 emails from this group listing precisions in the modern format
(ie, NTP-4.2.x), a histogram [1] of results is:

46 precision=-19
16 precision=-20
12 precision=-14
8  precision=-18
4  precision=-8
3  precision=-15
3  precision=-10
2  precision=-16
1  precision=-21
1  precision=-13
1  precision=-19
1  precision=-10

One might do better using 'ntpq -crv' against published NTP servers or pool members to collect data.


[1]: grep -hr 'precision' _IMAP_storage_ | sed 's/3D-/=/g' | sed 's/> //' | sed 's/>//' | sed 's/==/=-/' | awk -F, '{print $1}' | histogram.py | grep 'precision=-'

...and then trimmed a few stray matches, such as the Subject: header of this thread.

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