On Mar 4, at 19:44 I wrote: > I released another test version today onhttp://davehart.net/ntp/refclock/ > Contrary to my previous claim, my recent versions have not been using > the observed performance counter frequency instead of the nominal one > from QueryPerformanceFrequency. A range-gate in my code to observe > the performance counter was preventing any changes silently. This had > apparently been the case since I switched to the new interpolation > strategy. Today's version re-enables the tuning and seems to have > knocked a bit more jitter out of the interpolated time in my case. > The nominal frequency is used for the first 36 minutes as four 512 > second samples of the observed counter frequency are collected, then > the observed value is switched into use and updated every 512 seconds > thereafter. This resulted in cutting short-term jitter in half > (observed as a vertical smearing of the offset graph line).
http://davehart.net/ntp/refclock/loopstats-20090304-tune-ctr-freq+44ppm-at-2154.jpg or http://tinyurl.com/dmp58p That's a one-hour before and after snapshot of my refclock test machine with the transition to using the observed counter frequency in the middle at 21:54. I hope the coincident 90 usec step is a fluke. The short-term jitter before and after is encouraging, looks like from over 20 usec to under 10. Cheers, Dave Hart _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
