[ntp:questions] nmea and initial large offset

Dave Hart hart at ntp.org
Sun May 23 12:43:02 UTC 2010

On Sun, May 23, 2010 at 09:40 UTC, David Woolley wrote:
> Dave Hart wrote:
>>> I'm afraid i have to add a workaround in my application which also gets
>>> the gps input,
>>> to set the time when it's more then 4 hours away from gps time.
>> I think a better answer is to disable ntpd's "panic" threshold
>> entirely with "tinker panic 0" in ntp.conf.
> I thought the panic limit was 1,000 seconds.  Has this been changed?

No.  Unless, of course, you use "tinker panic", in which case it's
whatever you specify, and 0 has the special meaning "never panic
exit". http://www.eecis.udel.edu/~mills/ntp/html/miscopt.html#tinker

> I thought the 4 hours was a new limit, that applied even if told not to
> panic on the first setting.

Not new, but different, yes.  This 4 hour tolerance, as has been said
repeatedly in this thread, comes from the decision to not use any year
information provided by the reference clock driver, but instead infer
the year based on the other date and time components.  In the case of
a GPS NTP appliance with zero memory of the time available at startup,
you need not only "tinker panic 0", but also to hack around this
year-guessing code to relax the 4 hour limit.

Dave Hart
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