[ntp:questions] Sure GPS - Very High Jitter and Offset

Miroslav Lichvar mlichvar at redhat.com
Tue Aug 16 10:52:30 UTC 2011


On Mon, Aug 15, 2011 at 10:58:45PM -0500, Ken Link wrote:
> Now, I get timestamps in the assert and clear files: 1313465775.004708342#4545
> 
> However, the source is still jittery! 15ms sometimes, like it's not
> using the PPS signal at all.

If you compare few assert timestamps in row, how stable is the offset?
Couple of microseconds?

> The important configuration lines are:
> server 127.127.20.0 mode 18 minpoll 4 prefer
> fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 flag4 0

You wrote earlier that you use a 2.6.38 kernel. I think the kernel PPS
discipline was added later, so maybe it would help to remove the flag3
setting.

Also, how is marked the PPS source in ntpq -p output?

-- 
Miroslav Lichvar



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