Geoff Powell said the following on 04/23/2006 05:42 PM: > Is PPS kernel discipline compiled into the default FreeBSD kernel?
No, but it's a pretty easy thing to turn on -- you add a line to the config file and tell it to go. Pretty straightforward, *once* you find the instructions. > > >>I am not running 2.6.15 because it has some problems with the linux-gpib >>drivers that I depend on for data logging, but instead using a shared >>memory driver called "shm_linux_clock" that runs as a separate program >>and monitors a serial port for PPS and passes that through to NTP. It >>works very well and holds within 10s of microseconds, most of the time. > > > Does this require a kernel recompile, is it a module, or does it run in > userland? It runs in userland. You need to make sure that your NTP has the shared memory refclock compiled in. > Yes, I noticed that all the machines vary more-or-less together, which > suggests a common-mode effect - is databox playing up? Yes, yesterday databox suffered an unplanned reboot, which exposed some configuration problems. It took quite a while to get everything playing properly, and then NTP takes a while to settle down. I have a Soekris 4501 on order (do you detect a theme?) and plan to lock its oscillator to the house timebase, and then switch the monitoring task over to that machine and away from databox. For now, I get a sense of how databox is performing by looking at the common mode effect on the other servers. > > I know that radio clocks (I'd be using MSF Rugby, or DCF Mainflingen) > are poor in comparison, and probably worse than your WWVB results, > because the receivers I'd be using would have a lot less intelligence > than yours. > I don't know -- the Spectracom receiver is pretty ancient technology, and I suspect that Jonathan Buzzard's code running on a modern machine might give it a good run for its money. The biggest problem with the Spectracom is that when it loses lock once every 10 days or so, there is a sudden multi-millisecond offset that takes a couple of days to fully recover from. John _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts