[ntp:questions] NTP on Windows Vista

David J Taylor david-taylor at blueyonder.neither-this-bit.nor-this-bit.co.uk
Fri Jun 20 09:18:26 UTC 2008

David Woolley wrote:
> David J Taylor wrote:
>> Yesterday I undated my Windows Vista system to Service Pack 1, and
>> whilst NTP initially appeared to work correctly, it soon developed
>> an oscillating state.  See:
>>   http://www.satsignal.eu/ntp/NTP-on-Windows-Vista.html
> They look like damped oscillations, so the questions are:
> - why are you getting time steps;
> - why is the response not critically damped.
> Can I just confirm that this system is connected to its time sources
> only by ethernet, and that that ethernet has low latency drivers? Apart 
> from that one might suspect some complex power management
> feature.
> Under damping tends to indicate that ntpd is miscalculating the
> frequency correction.  On Windows, the API it uses directly controls
> the software clock rate.

Thanks for your reply, David.

Yes, the only connections to time sources are via Ethernet, and this PC 
used to be fine when it ran Windows XP with a very similar configuration. 
You can see what it was like last year, before November when Vista was 
installed, here:


The ntpq output shows that it is synced to my stratum-1 server.  Other PCs 
work well from this same server:


According to SIW (System Information for Windows) the clock interrupts are 
at 15msec intervals.  As far as I know, the only power management is on 
the display, which is switched off after 20 minutes.  No disk power-down, 
or hibernation.

I had wondered if there was any clue in "it seemed OK immediately after 
reboot", or whether that was just luck.


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