[ntp:questions] Clock jumps 1 second every 11 minutes (Linux+SMP+NTP)

Nathan Parker google.20.nathanpll at spamgourmet.com
Mon Aug 25 20:10:05 UTC 2003

I'm trying to syncronize the clock on a dual-processor DELL 2600 with
3.06 GHz Intel XEONs.  It's running Linux (RH7.3) with
2.4.18-27.7.xsmp kernel and NTP v4.1.1.

Without NTP, the clock drifts 1.07 seconds slow per hour.  With NTPD
running (to a strat 1 server) with the -x1 option, the clock JUMPS
FORWARD one second every 11 minutes exactly -- it keeps doing this,
even when the clock is 20+ seconds fast! Without the -x option, the
clock still jumps forward but then NTP jerks it back again a moment
later. I've let it run for days and it never stabilizes. This is very
disruptive to the real-time signal processing I'm trying to do on this

I dug in the linux kernel source and found that it (apparently) sets
the BIOS clock from the Linux RTC every 11 minutes -- is this "11
minutes" a coincidence, or is it related?  What can I do to keep
proper time on this machine?

 -- Nathan Parker

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