Quoting Joachim Fabini <joachim.fab...@tuwien.ac.at>: :
I'm really surprised, that's excellent. Do you have any figures how ntpd performs when using this PPS source? My earlier comment was relying on the assumption that the diagram displays the ntp log (loopstats) statistics. Until now, with Linux, desktop computers and rather expensive GPS equipment I couldn't get the system clock's offset better than +-5µs over some hours. Publications point out that the CPU performance has major influence on the ntp timesync accuracy, too. The PPS reporting is a different story but still a main prerequisite. Can you share some results on ntp loopstats based offset?
Here's some data from my systems. I'm using chrony, but this is from the equivalent logfile to ntp's loopstats. These are histograms of all local clock offsets over the past 7 days.
Beaglebone Black + NS-T GPS + pps_gmtimer.ko: http://dan.drown.org/bbb/run23/offset-histogram.png
50% of the time, the local clock's offset is between -0.03us and +0.02us. 98% of the time, it's between -0.34us and +0.36us. The maximum offsets were -3.28us and +2.91us
Raspberry Pi + Navspark-GL GPS + pps_gpio.ko: http://dan.drown.org/rpi/run6/offset-histogram.png
50% of the time, the local clock's offset is between -0.12us and +0.17us. 98% of the time, it's between -1.63us and +1.04us. The maximum offsets were -5.69us and +3.18us
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