A histogram of the frequency samples: http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/freq-hist.png The x positions are fudged by 0.02 Hz so multiple dots on the same point don't land on top of eachother and hide the ones on the bottom.
Another dip big enough to get below 59.9 Hz: http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/2014-Jan-26-a-dip.png An example of a bug: http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/2013-Dec-26-a-bug.png The kernel code that collects the data and prints it via the /sys file system is missing a lock. Occasionally, the count is off by one. I assume the printout code gets the new time and old count. That turns one of my samples into being low in frequency and the following one being high in frequency. The offsets are big enough to stand out. [I haven't looked at the code to verify this.] This also provides an overall sanity check. If counts are getting lost due to interrupts being locked out for too long, that will stand out like this. Similar for extra counts due to noise. -- These are my opinions. 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.
