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

Martin Burnicki martin.burnicki at meinberg.de
Wed Dec 7 11:21:19 UTC 2005


Sorry for the late response, I've been offline the last few days.

David J Taylor wrote:
> Thanks for that observation, Johan.  Thursday's events could well have
> been the cause, this is what happened (approximately):
> - I looked at an animation - QuickTime said there was a newer version
> available.
> - I downloaded the newer version
> - on starting to install the newer version, I noted it installed iTunes
> - as I have no need for iTunes, I stopped the install
> Now perhaps this left things in a half installed, half not installed
> state?  Later, I did remove QuickTime entirely and re-install V6.5.2 (with
> no iTunes) from a file I already had on disk.

This points to the problems with Windows time if a multimedia application is
started. I've mentioned this sometimes before here in the newsgroup, e.g.

This problem is NOT from the MM apps themselves but from the way Windows is
keeping time, and AFAIK has been fixed by MS in SP2 for WinXP.

So you won't fix the problem by using another version of ntpd. Either you
must make sure no MM app runs at all (maybe even not in the background, if
QT looks if updates are available), or you must have at least one MM app
running continuously in order to have the MM timer set constantly set
either to highest resolution or default resolution, but not switching
between the 2 resolutions. 

If the MM timer is set constantly to high resolution then you should observe
a little more jitter than with default resolution, but the large steps
should go away. So as a test you just might to start Quicktime ant watch if
the offset settles down.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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