[ntp:questions] Getting NTP to correct only the clock skew
Spoon
root at localhost.invalid
Sat Mar 31 11:52:15 UTC 2007
Steve Kostecke wrote:
> Spoon wrote:
>
>> Is it possible to run NTP in a mode where it does not try to correct
>> the time offset, but only correct the frequency offset (skew)?
>
> Yes.
>
> Provide your ntpd with a stable PPS source and use the Undisciplined
> Local Clock.
I am running Linux 2.6.20.3-rt8
I don't think vanilla 2.6 supports PPS sources at the moment?
http://lkml.org/lkml/2007/2/16/303
Surely there must be some experimental patches?
http://unix.freshmeat.net/projects/ppskit/
http://www.kernel.org/pub/linux/daemons/ntp/PPS/
In my situation, I don't care what time it is, but my clock needs
to tick at the correct rate.
I've found the following articles:
http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm#S-CONFIG-ADV-PPS
http://www.cis.udel.edu/~mills/ntp/html/pps.html
Can you suggest additional resources?
I think I can't use GPS because the computer is located in
a server room underground.
Are there other PPS sources? I've read about rubidium and cesium clock
sources. How expensive are they? Do they come on a PCI board that can
fit inside a 1U case?
Regards.
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