[email protected] said: > As far as NTP is concerned, I wonder if you've ever considered turning the > tables on how it works. AFAIK, NTP gets an external time reference (e.g., > 1PPS) as an interrupt. With modern computers, this is horrible. There are > far too may layers of h/w jitter (pipelines, multiple levels of cache, TLB > misses, etc.) and s/w jitter (interrupt handling, spinlocks, interrupt > masking, priority levels, etc.).
You have to have your time-nut hat on before that makes a difference. Has anybody measured it? It should be easy to hack the kernel PPS interrupt routine to flap a printer port signal and measure the delay between the PPS signal and printer port. > For best timing, perhaps a better solution is not to have NTP receive a 1PPS > as *input* and try to pretend to measure it internally in s/w but for NTP to > *output* a 1PPS and measure that externally with sub-microsecond h/w (like a > picPET). The Trimble Palisade and Acutime work that way. -- 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.
