I'm a bit unclear about how a refclock is supposed to specify how accurate it is. There are the delay and precision options. I think I understand what the docs say about delay. But I'm less clear about precision. What are the semantics of that, how does it impact what chrony does and how is it related to delay? The other thing I'm not clear about is how the precision and delay relate to the figure shown for the margin of error (after +/- in the last column of the chrony sources output).
As a concrete example, for a PHC extpps source (with no link to anything) connected to the PPS output of a GPS whose datasheet specifies a 30ns RMS accuracy, what should I specify for delay and precision and how do I get a sensible figure for margin of error? I've tried various figures in the range 10ns-100ns for delay and precision, but the margin of error remains in the 700ns-800ns range. The margin of error figure is similar to the dispersion figure in the refclocks log, so I'm guessing that's the main cause. Why is the dispersion so large and is there anything that can be done to fix it? At the other end of the scale, for a SOCK refclock for GPS messages where there's say 0.1s variation in the time the message is received, what is the right thing to put in refclock so that chrony won't treat it as a false ticker? Would it be delay 0.2? Is precision relevant here? James -- To unsubscribe email [email protected] with "unsubscribe" in the subject. For help email [email protected] with "help" in the subject. Trouble? Email [email protected].
