[time-nuts] NTP, PPS and < 10 us offsets
Hal Murray
hmurray at megapathdsl.net
Wed May 15 07:51:07 UTC 2013
albertson.chris at gmail.com said:
> Maybe not you, but I think some people think "Oh my, NTP is not checking the
> time very often. It must not be accurate." That is thinking backwards,
> you need the long poll interval to see small errors in rate. But this
> assumes a stable local clock. NTP balances this.
That "balance" is assuming a classic ADEV type V curve. That assumption
works better in old non-green systems that burned lots of power in an idle
loop when they didn't have any work to do. With modern systems, it's easy to
change the temperature significantly by starting/finishing a big chunk of
work.
External temperature changes can also be important. Every now and then, I
like to repost this link. This seems like a good opportunity.
NTP temperature compensation
http://www.ijs.si/time/temp-compensation/
--
These are my opinions. I hate spam.
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