[ntp:questions] Is 24PPM an Excessive Real-Time Clock Correction?

Martin Burnicki martin.burnicki at meinberg.de
Fri Jul 6 08:33:05 UTC 2007

David T. Ashley wrote:
> "Richard B. Gilbert" <rgilbert88 at comcast.net> wrote in message
> news:468D4A70.9030508 at comcast.net...
>> 24 PPM is pretty good.  Anything up to a hundred or two will usually work
>> just fine.
> Thanks.  Interesting.  It seems to be a really steady error, i.e. seems to
> always be between 24 PPM and 24.5 PPM.

The value in the driftfile indicates how much your system time would drift
if it was _not_ disciplined by ntpd.

Ntpd tells you which value it has determined, and as long as it is running
the drift is compensated as good as possible.

The mean absolute value depends on how much the xtal's frequency is off it's
nominal frequency. This is an individual value for an individual xtal on a
mainboard. As already mentioned in other replies, the actual frequency
varies with temperature +/- around that mean value.

As long as the value is in the range ntpd can handle (+/- 500 ppm)
everything is fine.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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