[ntp:questions] Re: is there a way to "lock" the drift frequency

wayne wayne at midwestcs.com
Thu Nov 20 01:02:59 UTC 2003

In <vrlm35i5dsutc6 at corp.supernews.com> hmurray at suespammers.org (Hal Murray) writes:

> I'll take your word for it, but I don't see lost interrupts
> discussed here very often.  Do you also have problems with
> lost characters on serial ports?  (and similar things)

Lost timer interrupts will normally only cause small blips on the ntp
log.  With a HZ value of 100, a jump of 10ms on the clock isn't going
to be very noticeable.

Timer interrupts happen *a lot*.  Very few other devices will generate
100 interrupts per second, every second, all day long.  If even a very
small percentage of them get lost, you are still going to prevent ntpd
from keeping as good a time as it could.

Timer interrupts have no buffering to fall back on.  A UART generates
an interrupt when there are still several characters free in the
buffer, so a lag of 10-20ms is no big deal.  Most other I/O devices
are similarly buffered.


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