Here is a typical 2 day view. http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-Jul11-12.png http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-Jul11-12-freq.png
Note that there are 3 interesting events visible on the frequency graph. More on those later. ---------- I think this is a generator dropping off-line, or something interesting at the main power production level. http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g11.png http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g11-freq.png That happens at about 4 hours on the above pair of graphs. On the offset graph, it's just a tiny glitch. It's much easier to spot in the frequency graph. Here is another similar event: http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g29a.png http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g29a-freq.png It took 0.07 hours (4 minutes) for the frequency to get back to normal. During that time, the system lost 13 cycles or over 0.2 seconds. ---------- Here is a typical extra cycle event. This one is actually 2 cycles. http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g12.png http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g12-freq.png It's about 16 hours on the above graphs. Here is another extra cycle: http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g13.png http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g13-freq.png This is about 27.5 hours on the above graphs. ------------ Here is a time step on the machine collecting the data. http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g14.png http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g14-freq.png I was downloading a huge file. That added a lot of queuing delay on my DSL link. After a while, ntpd decided the delayed version was the correct time and shifted to it which produced a 1/4 second offset. After another hour the download finished and ntpd shifted back to the correct time. 1/4 second at 60 Hz is 15 cycles. 1/4 second out of 10 seconds at 60 Hz is 1.5 Hz. [I have good time locally. I left that laptop running off network time servers so I could see things like this and/or other glitches I didn't anticipate.] ---------- This looks like a glitch in the PPS data collection code. I think it got the new time-stamp with the old count. http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g29.png http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz-g29-freq.png My guess would be a missing lock or disable interrupts. I've only seen one of these over roughly 2 months. The extra cycle events are more like 1 per day. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
