[ntp:questions] nmea and initial large offset

Richard B. Gilbert rgilbert88 at comcast.net
Sat May 8 13:56:29 UTC 2010


Rob wrote:
> Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
>> The clock CHIP is not the problem.  The problem is that the quartz 
>> crystal that provides the "tick" is usually one that failed quality 
>> control at a wristwatch factory.
> 
> The issue under discussion is not the accuracy of the clock, but the
> "fact" that it does not provide the year, only month/day/h/m/s.
> 
> I don't know about a chip that does not provide the year, but probably
> it existed in some obscure computer more than 20 years ago.
> 
> I know the chip used in early PCs had only 2 year digits and thus could
> not provide the century information, but I consider this a non-problem
> as it can be easily worked around by having some threshold value above
> which the year is considered in the past century (e.g. 80).
> 
> Defending silly algorithms in code with limitations in old hardware no
> longer in use in running systems seems a bit silly to me.
> 
> But I often recognize a pattern where people who operate ntpd in different
> environments than the one envisioned by the author get turned away when
> suggesting changes.
> We all know the discussions about systems not running 24h/day, systems
> with instability related to temperature that changes over a day/night
> pattern, arbitrary nonconfigrable limits on clock drift, initial clock
> offset etc.

Please feel free to design your own algorithms to deal with the "systems 
not running 24h/day" and, while you're at it, deal with temperature 
variations and support drift rates up to 5,000 PPM, etc, etc.

NTPD, when used as intended keeps time very well!




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