[ntp:questions] Server sync changed from 3ms to 75ms

holmezy at yahoo.com holmezy at yahoo.com
Thu Jan 6 18:55:32 UTC 2005

Hello everyone,

Some of our IBM Regatta P690 servers recently started displaying time
differences of +/-75ms in the past six weeks.  Prior to this the time
differences were +/-3ms.  These systems are managed under very strict
CM guidelines!

Each Regatta has its own TrueTime NTS100i timeserver and each one is
running xntpd.  The TrueTime servers receive an IRIG-B input signal
from one upstream GPS unit.  Prior to the start of our software a
"timedc clockdiff hostname1 hostname2 hostname3" is performed to verify
the that the Regatta sytem clocks are within a +/-3ms tolerance.

We've been running the same config in the lab for a few years and noone
has ever seen this problem before.  The only change to the config in
recent memory is the addition of 1 more Regatta, with its own
timeserver to the mix.

Any thoughts or suggstions on where to look for some better info?
We've tried various commands such as ntptrace, ntp -q, etc.  We're in
the process of verifying the IRIG-B input signal to the TrueTime
machines.  I don't believe this will yield much as all the TrueTime
machines are connected to the same signal amplifier.  I have a call
into IBM with a system clock question regarding a similar problem we've
had in the past.  Apparently, there is some validity to my concern but
haven't heard back from the Development Engineers.
Thanks in advance,

John Holmes

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