[ntp:questions] soekris 4501 that won't settle

Joshua Coombs jcoombs at gwi.net
Tue Mar 21 04:22:25 UTC 2006


My nanobsd testbed has decided to drive me up a wall.  When I set it 
loose, it starts hunting for a pll adjustment value, swinging wider 
and wider with each period.  When I last restarted ntpd to try a conf 
change, it was varying the pll freq by 40ppm over the course of one of 
it's sweeps.

Plotting the adjustment value over time generates a lovely sine wave 
with a static period but an exponentially growing amplitude centered 
on -25ppm.

The box is running FreeBSD 6.1B4, and I've alternated between the base 
included ntpd (4.2.0a) and the 4.2.1RC and both show the same 
behavior.  I was initially locking the poll interval at 2048 seconds 
as this is a test setup and I both wanted to verify the stability of 
the 4501 and keep from abusing the remote servers I was using.  I've 
lowered it to 512 seconds to see if that improves things...

Any suggestions on where to look for the cause?  I picked 4501s based 
on PHK's write-ups covering their excellent timekeeping abilities, and 
am not seeing it in practice so I'd like to know where I err'd.

Joshua Coombs 




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