[ntp:questions] Red Hat vote for chrony

Charles Swiger cswiger at mac.com
Tue Dec 9 18:30:35 UTC 2014


On Dec 9, 2014, at 2:41 AM, Terje Mathisen <terje.mathisen at tmsw.no> wrote:
[ ... ]
>>> Yes; you're describing calibrating a temperature-compensated XO, or TCXO.
>> 
>> There are also versions of ntp which have a temp
>> compensation/measurement system compiled in to apply to the clocks. It
>> does tend to give much better control of the clock than regular ntpd
>> apparently.
> 
> It does help:
> 
> On motherboards with a temperature sensor close to the master crystal, you can get somewhere in the 2-10x range improvement in the size of temperature excursions.

I'd agree with this, although the best case is probably not quite an
order of magnitude, more like a factor of 5x.  Or perhaps I shouldn't
be too optimistic about how bad a really cheap crystal can be.  :-)

> The correct solution is of course to not depend on $0.10 crystals as the time base for dedicated NTP servers. :-)

Well, yes.  You can get a PCI(e) card with a TCXO or OCXO and an
optional GPS module like the Beagle ClockCard or a SpectraCom TSync
for a few hundred bucks.

That's quite a bit more than a $40 GPS puck, but these will also
freewheel for a lot longer before losing or gaining a second in
error: ~2 seconds/month if kept stable at 23C, I believe one said.

Regards,
-- 
-Chuck



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