On Apr 17, 10:03 am, lellis <larry.el...@gmail.com> wrote: > > With the help of several radio-controlled clocks in my office, I > noticed that the local clock on my machine was occasionally off by > exactly one second (sometimes slow, sometimes fast). > > While I'm not sure this is the definitive answer, the following > changes seem to have helped: > > 1. I configured the Garmin to output both an RMC and a GGA sentence. > > 2. Using a small com port test program I wrote, I determined that the > GGA end-of-line is received about 850 ms after the leading edge of the > DCD pulse > > 3. I then modified my configuration file to include a time2 value of > 850 ms: > > server 127.127.20.1 mode 2 minpoll > 4 #mode 2, use GPGGA > fudge 127.127.20.1 flag1 1 time2 > 0.850 #time2 compensates for GGA offset > > I also deleted my drift file before restarting. > > I am now using a very recent build (4.2.7.p150) without apparent > problems. > > Larry Ellis
As what will probably be a final update to this issue, the +125ms difference I reported initially *did* reoccur with 4.2.7p150. After several days of running with low milliseconds of difference between all reference sources, the +125s for the Atom PPS driver reappeared. Note, that the positive offset did not effect the user- mode PPS timing, which was still spot on: remote refid st t when poll reach delay offset jitter ============================================================================== *GPS_NMEA(1) .GPS. 0 l 9 16 377 0.000 0.981 0.016 PPS(1) .PPS. 0 l 10 16 377 0.000 126.063 0.16 (other offsets < 5 ms) In effect, this tells me the offset between the user-mode PPS and the serialpps.sys PPS driver is about .125s (I was using flag1=0 to disable use of the kernel mode PPS). Since this odd recurrence was using software which heretofore had *not* shown the issue. I tried rebooting my system. It did not solve the problem (.125 offset still presented itself). I then cold-started the system, and the user-mode PPS and kernel-mode PPS offsets reverted to sub-millisecond range. So while the reason for this is unclear, a simple cold-start of the system accomplished what a warm reboot did not. This leads me to believe what I was seeing is likely a quirk of some kind in my hardware configuration. Thanks again to everyone who tried helping me with this. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions