[ntp:questions] Re: ntp.drift
david at djwhome.demon.co.uk
Fri Jan 28 07:51:54 UTC 2005
Walter HILL wrote:
>The computer was losing about 2s / hour prior.
2s an hour is more than the 500ppm capture range for ntpd.
You either have a broken motherboard (good quality ones will be
within 50ppm and even the worst I've seen are within about 200ppm) or
you are losing a lot of clock interrupts.
In the broken motherboard case, replace it.
Lost clock interrupts are particularly prevalent on Windows and on
Linux. For Linux the problem is that Linux device drivers often disable
interrupts for rather a long time and at the same time recent versions
of Linux have started using 1ms clock ticks, rather than 10ms ones. This
has been extensively discussed over recent weeks on this newsgroup, but
as a general principle, you cannot hope to maintain good time on a machine
that is losing large numbers of interrupts, as the exact loss rate isn't
ntp.drift isn't being updated because you never achieve frequency lock.
ntpd is not a solution for broken systems.
More information about the questions