[ntp:questions] 500ppm - is it too small?

David Woolley david at ex.djwhome.demon.invalid
Thu Nov 12 22:58:40 UTC 2009

Uwe Klein wrote:

> A:
> An off by 1000ppm xtal is not an easy reason
> for exchanging motherboards with your vendor.
> B:

It pretty much has to be broken, as it is so far outside the production 
spread that is unlikely to be working reliably.

> An off by 1000ppm xtal is differently broken
> from one that wanders up and down the ppm range
> on changes of barometric pressure, humidity and
> other whimms.

That is even more definitely broken.  It pretty much guarantees a major 
structural defect.

> Thus if satisfying timekeeping hangs on 500ppm being
> a limit the next best step is to push on the software.
> "Software" as the word says is regularly the less
> resilient target for problem solving ;-)

There already is a software solution on most systems that run ntpd.  You 
can correct the frequency in multiples of 100 ppm, from completely wild 

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