I'm trying to figure out why my FreeBSD 9.0-STABLE system with a Garmin GPS 18x LVC and ntpd 4.2.7p255 has a consistent -2 ms to -4 ms offset from most other servers. This is clearly evident in its pool graph: http://www.pool.ntp.org/scores/2001:470:8683:0:219:b9ff:fe7d:e6e0
The offset seems to correspond to the PLL offset, which I have munin graphing: http://kenyonralph.com/munin/kenyonralph.com/gauss.kenyonralph.com/ntp_kernel_pll_off.html Most other systems [0] (including my own) seem to hover around zero, but this one with the GPS hovers around -2 ms. Any ideas on how I could correct this? Could this just be a case of bad computer hardware? It's a Dell Latitude D520, which has a serial port. It seems to be very consistent and stable, just offset! Thanks. $ cat /etc/ntp.conf statsdir /var/log/ntp statistics clockstats loopstats peerstats leapfile /etc/ntp/leap-seconds.list server 127.127.20.0 minpoll 3 iburst fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 time2 0.545 server darwin.kenyonralph.com iburst server voodoo.kenyonralph.com iburst server grunt.kenyonralph.com iburst # stratum 1 server clock.fmt.he.net iburst server tick.ucla.edu iburst server time.xmission.com iburst server ntp.exact-time.org iburst server ntp.your.org iburst # stratum 2 server clock.psu.edu iburst server ntp2.jtsage.com iburst server tick.mattnordhoff.com iburst $ ntpq -p -c clockvar -c readvar -c kerninfo remote refid st t when poll reach delay offset jitter ============================================================================== oGPS_NMEA(0) .GPS. 0 l 7 8 377 0.000 0.000 0.002 +darwin.kenyonra 127.67.113.92 2 u 55 64 377 20.557 1.124 2.819 voodoo.kenyonra 94.78.119.192 2 u 63 64 377 0.283 0.870 0.062 grunt.kenyonral 94.78.119.192 2 u 15 64 377 0.175 0.512 0.029 *clock.fmt.he.ne .CDMA. 1 u 27 64 377 21.668 1.524 3.522 +tick.ucla.edu .GPS. 1 u 48 64 377 31.787 2.096 2.587 +2607:fa18::2407 .GPS. 1 u 18 64 377 42.634 2.584 2.715 +ntp.exact-time. .GPS. 1 u 55 64 377 201.559 2.013 2.477 +ntp.your.org .CDMA. 1 u 65 64 377 72.936 1.430 2.342 -otc2.psu.edu 147.84.59.145 2 u 63 64 377 104.272 3.331 1.490 -ntp2.jtsage.com 127.67.113.92 2 u 18 64 377 60.644 -0.267 3.316 +tick.e.mattnord 129.7.1.66 2 u 56 64 377 61.508 0.707 3.306 associd=0 status=0000 no events, clk_unspec, device="NMEA GPS Clock", timecode="$GPGGA,221921,3259.1559,N,11714.2761,W,1,08,1.1,101.0,M,-35.3,M,,*7E", poll=75537, noreply=0, badformat=0, baddata=0, fudgetime2=545.000, stratum=0, refid=GPS, flags=5 associd=0 status=0419 leap_none, sync_uhf_radio, 1 event, leap_armed, version="ntpd [email protected] Sat Feb 4 07:17:31 UTC 2012 (1)", processor="amd64", system="FreeBSD/9.0-STABLE", leap=00, stratum=1, precision=-19, rootdelay=0.000, rootdisp=1.105, refid=GPS, reftime=d318c6e1.cdf93c61 Sat, Mar 24 2012 15:19:13.804, clock=d318c6e9.9752b956 Sat, Mar 24 2012 15:19:21.591, peer=6248, tc=3, mintc=3, offset=-0.000, frequency=-4.243, sys_jitter=0.002, clk_jitter=0.001, clk_wander=0.000, tai=34, leapsec=201207010000, expire=201212280000 associd=0 status=0419 leap_none, sync_uhf_radio, 1 event, leap_armed, pll offset: -0.000352 pll frequency: -4.24277 maximum error: 0.005 estimated error: 0 kernel status: pll ppsfreq ppstime ppssignal nano pll time constant: 3 precision: 1e-06 frequency tolerance: 495.911 pps frequency: -4.24277 pps stability: 0.00227356 pps jitter: 0.001 calibration interval 256 calibration cycles: 18526 jitter exceeded: 75927 stability exceeded: 0 calibration errors: 9 [0] https://www.google.com/search?q=munin%20NTP%20kernel%20PLL%20offset -- Kenyon Ralph
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