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

Ulrich Windl Ulrich.Windl at RZ.Uni-Regensburg.DE
Thu Nov 12 12:15:48 UTC 2009


"David J Taylor"
<david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid> writes:

[...]
> Ulrich,
>
> So machine running other than Windows don't suspend?  In any case, it was more
> the clock-speed variation I was thinking of.
>
> But I note that you think 500ppm is enough.

[Skipping the part where you are saying I'm insulting]

Yes, as even most mechanical wrist-watches are better than the 500PPM
that NTP allows, I'm really getting tired of people trying to fix the
broken hardware clock with software, just because the hardware vendor
saved a few cents on the crystal. Also, NTP (and possibly operating
system's time routines as well) was never designed for
machines that use variable clock frequencies. So I assume: If you really
care about a clock that is closer than 100ms to the real time, you'd use
the proper hardware with NTP. Otherwise use something else.

IMHO, most people don't care if their clock is a few minutes off, but
with using NTP they suddenly expect that their clock will automagically
become as good as an atomic clock.

Ulrich




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