[chrony-users] Multi-PPS+RTC Setup Questions

[Matt Corallo <ntp-lists@xxxxxxxxxxxxxxx>]

I have a setup with two GPS receivers with PPS inputs as well as a local RTC that is (roughly) disciplined to GPS time 
as a sanity check.

From the docs, I'd expect to set this up as, roughly

refclock ...RTC precision 0.002 trust require
refclock PPS refid GPS1 ... prefer
refclock PPS refid GPS2 ... prefer

but on chrony 3.4 this seems to result in lots of reselection, with chrony often selecting the RTC as the current clock 
source (with or without the prefer set on the PPS refclocks), even when the GPS PPS refclocks are well within the 2ms of 
the RTC and the stddev of the GPS clocks is 1.5 orders of magnitude lower on the GPS refclocks.

If I drop "trust" on the RTC, it seems chrony 3.4 will happily decide NTP time is more than 2ms away from the RTC even 
though it may not update the system clock for it (separately, I should probably figure out why my two independent, 
different-model GPS receivers occasionally decide to jump 2-5ms for 10-20 seconds at a time).

If this is just an old-chrony-version issue I'm happy to try to build 4.0, but I figured I'd ask what the right settings 
are first.

Finally, it would be nice to get a warning if "maxlockage" is not set when rate is >1 - if I'm understanding it 
correctly it doesn't make sense to have a rate > 1 if the lock source doesn't have a negative dpoll (which should 
roughly be the common setting for eg a GPS set  to >1HZ PPS, as in my setup).

Thanks,
Matt

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