[ntp:questions] Re: Windows timekeeping - sudden degradation - why?

John Allen allen{at}vo{dot}lu at ntp.isc.org
Mon Dec 12 22:14:53 UTC 2005

Richard B. Gilbert wrote:
 >Do you have a drift file?   What value is stored in the drift file?
 >What was the interval between the two ntpq -p commands?

 >My guess would be that your local clock has a frequency error well in
 >excess of 500 parts per million!   If that is the case, you will
 >probably have to replace the mother board to fix it.


Sorry to respond so slowly on this. Your message didn't appear on the newsgroup 
server I was using, and I only found it today when I was browsing back through 
the thread on Google Groups.

I had missed the significance of the fact that the drift file has regularly been 
up to -500.00 at which point NTP really does give up - so the irregular 
time-keeping was not from NTP but from the PC's system clock unsynchronised by 
NTP. This was happening very quickly - the interval between the successive ntpq 
-p commands was only ten or fifteen minutes.

As you say, the hopeless inaccuracy of the system clock might be cured only by a 
new motherboard, although it seems strange that for more than a year it seemed 
to work fairly well.

Along the way I discovered this useful Windows command:

w32tm /stripchart /computer:barlow /dataonly
(barlow is my server, running NTP)

which just prints the successive offsets - a kind of text-only version of David 
Taylor's  NTPMonitor. As it doesn't require NTP to be running, it is a 
convenient way to see what the system clock is doing - on my system, the results 
are not encouraging.



John Allen
Bofferdange, Luxembourg

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