Dave, The NTP discipline executes a frequency correction once per second; the kernel executes a correction once per timer interrupt. Assume an intrinsic oscilator frequency error of 100 PPM. Do the math.
Dave Dave Hart wrote: >On Mar 25, 9:19 pm, Unruh <unruh-s...@physics.ubc.ca> wrote: > > >>I have no idea why and whether kernel PPS code is any better ( or worse) >>than say PPS discipline using the shm PPS refclock using parallel port >>interrupt. Ie, both can discipline >>to about 1-2usec level. >> >> > > >Re-read the thread, then. A kernel clock disciplined by PPS allows >PPS to continue to discipline the clock when ntpd's PPS implementation >stops doing so because of a prefer peer problem. > > > > >>The main problem is that the ntp model is too slow >>reacting to temperature induced drifts. >> >> > > >I'm sure that's your main problem re ntpd, but it's completely >tangential to the thread. > > > > >>>The complete system doesn't serve time to others. It's intention is >>>monitoring. I'm building this as a diploma thesis for a >>>telecommunication company. They have a large number of ntp servers >>>with GPS receivers (called SSU) across the country. So my system only >>>watches the offsets, that these SSUs have to assure that they are OK. >>> >>> >>They can monitor only to the msec (or 1/10 msec) level unless the other >>systems are at the same place. >> >> > > >I think he's monitoring the self-reported offsets between the NTP >disciplined clock and the local GPS receiver. Network delay would not >be a factor if so. > >Cheers, >Dave Hart > >_______________________________________________ >questions mailing list >questions@lists.ntp.org >https://lists.ntp.org/mailman/listinfo/questions > > _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions