John Ioannidis wrote: > Thanks for the reply, but this is not answering my question. I wasn't > asking how to *configure* the beast (I've already done this > successfully), I was asking how to verify that it actually works as > documented! > > What measurements do I have to take that will show the difference > between a setup that's actually using the PPS signal from the GPS > receiver and one that's not (because, for example, the DCD line on the > motherboard is cracked, to give a stupid example). > > Cheers, > > /ji
John, There is information on how I monitor here: http://www.david-taylor.myby.co.uk/mrtg/daily_ntp.html The GPS-locked accuracy is some three orders or magnitude better than Internet only. Compare the top graph (+/- 20 microseconds) and the lower graphs (+/- 100 milliseconds). In my particular case, with a limited view of the sky from quite far north (56 degrees), The drift which starts when there are too few satellites to allow the GPS-18 to declare "lock" is very obvious. You could simulate that by disconnecting the GPS, of course. My simple notes are here: http://www.david-taylor.myby.co.uk/ntp/FreeBSD-GPS-PPS.htm Search for the word "pixie" to see the effect of PPS_SYNC, with extra lines in the "ntpdc -c kern" output. Cheers, David _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
