[ntp:questions] Re: NTP with linux kernel 2.6.9 vs. kernel 2.4.24

David Woolley david at djwhome.demon.co.uk
Mon Jan 17 22:00:03 UTC 2005

In article <mailman.25.1105956066.588.questions at lists.ntp.isc.org>,
Goetz Lichtwald <lichtwald at tm.uka.de> wrote:

> ntpd[22804]: frequency error -512 PPM exceeds tolerance 500 PPM

Either you are losing a lot of timer interrupts (I can't remember
if this would be reported as a positive (correction) or negative
(error) value), or your motherboard crystal is way out.

In the former case, you must fix the device driver that is losing the
interrupts (or reduce the kernel interrupt rate - 100Hz, as on older
and slower systems, is usually OK).

In the second case, it indicative of hardware that is too unreliable
to use with precision time keeping, and you should replace the hardware,
although the use of the tickadj utility, to modify the kernel's idea of
the duration of a tick, can be used to compensate in multiples of 100ppm.

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