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

Martin Burnicki martin.burnicki at meinberg.de
Thu Dec 8 08:17:44 UTC 2005


David J Taylor wrote:
> David J Taylor wrote:
>> Martin Burnicki wrote:
> []
>>> 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 and watch if the offset settles down.
> []
> Well, with the MM timer permanently running (from 17:00 Wednesday) I can
> report that things are /much/ better, see:
>   http://www.david-taylor.myby.co.uk/mrtg/odin_ntp.html
> - the offset first shot up to 120ms, but is now gently decaying towards
> zero.
> - the jitter figures seem much better, around 1 (LAN servers) - 2ms (WAN
> servers).
> - the drift value has changed from -65 down to -9.3ms.

Those results are exactly what I've expected.
> I would certainly like the option, for this system at least, of running
> with the MM timers permanently in its high resolution mode.

Agreed. Maybe Danny and Harlan accept my patch. 

> I would also be interested in determining which program is switching the
> MM timer speed, and thereby upsetting the otherwise excellent timekeeping
> on this system.  I wonder if there's a relatively easy way to determine
> this?

Unfortunately there's no way to find that out, AFAIK. You can only observe
the effects indirectly. 

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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