[ntp:questions] Garmin 18 LVC high offset and jitter
David Lord
snews at lordynet.org
Mon Sep 19 08:21:44 UTC 2011
Miguel Gonçalves wrote:
> Hi all!
>
> I am having a problem with a Dell server that has a Garmin 18 LVC attached.
>
> It's a FreeBSD 7.4 machine with the Garmin 18 LVC connected to a serial port
> (PPS on DCD pin). The kernel has been compiled with the line "OPTIONS
> PPS_SYNC". NTP is 4.2.4p5.
>
> Here's the ntp.conf file:
>
> server 127.127.20.0 mode 2 iburst prefer
> fudge 127.127.20.0 flag3 1
>
> server ntp-p1.obspm.fr iburst
> server ptbtime1.ptb.de iburst
> server ntp.inrim.it iburst
> server ntp1.oma.be iburst
>
> server canon.inria.fr iburst
> server time.fu-berlin.de iburst
> server chronos.csr.net iburst
> server ntp1.nl.uu.net iburst
>
> statsdir /var/log/ntp/
> filegen clockstats file clockstats type day enable
> filegen peerstats file peerstats type day enable
> filegen loopstats file loopstats type day enable
> statistics clockstats peerstats loopstats
>
> logfile /var/log/ntp/messages
>
> restrict default kod nomodify notrap nopeer
> restrict 127.0.0.1
>
> I've disabled ACPI in /boot/loader.conf (hint.acpi.0.disabled=1) but did not
> disable serial FIFO.
>
> I am getting very high offsets and jitter for this reference clock:
>
> remote refid st t when poll reach delay offset
> jitter
> ==============================================================================
> *GPS_NMEA(0) .GPS. 0 l 40 64 377 0.000 -0.031
> 0.043
> +ntp-p1.obspm.fr .TS-3. 1 u 50 64 377 54.154 1.611
> 1.843
> -ptbtime1.ptb.de .DCFa. 1 u 119 64 376 70.069 -2.174
> 1.283
> -ntp.ien.it .CTD. 1 u 35 64 377 65.682 2.037
> 6.667
> -ntp1.oma.be .PPS. 1 u 26 64 377 61.911 2.280
> 3.673
> +canon.inria.fr .GPSi. 1 u 30 64 377 54.626 1.442
> 1.700
> -time.fu-berlin. .PPS. 1 u 32 64 377 73.342 -0.292
> 3.136
> -chronos.csr.net .GPS. 1 u 32 64 377 85.049 -3.656
> 5.096
> -ntp1.nl.uu.net .PPS. 1 u 2 64 377 67.085 3.435
> 3.888
>
> tick# ntpdc -c kerninfo
> pll offset: -7.886e-06 s
> pll frequency: -6.729 ppm
> maximum error: 0.030005 s
> estimated error: 6e-06 s
> status: 2107 pll ppsfreq ppstime ppssignal nano
> pll time constant: 6
> precision: 1e-09 s
> frequency tolerance: 496 ppm
> pps frequency: -6.729 ppm
> pps stability: 0.312 ppm
> pps jitter: 4.03e-07 s
> calibration interval: 256 s
> calibration cycles: 152
> jitter exceeded: 1029
> stability exceeded: 0
> calibration errors: 3
>
> It seems the internal clock of the machine is going nuts (small snippet of
> loopstats file):
>
> 55822 70649.300 0.000037529 -6.306 0.000000816 0.139388 6
> 55822 70714.307 0.000004089 -6.175 0.000001464 0.138376 6
> 55822 70779.307 -0.000029839 -6.175 0.000013699 0.129439 6
> 55822 70845.306 -0.000058655 -6.175 0.000000562 0.121079 6
> 55822 70909.305 -0.000078382 -6.175 0.000000570 0.113259 6
> 55822 70972.305 -0.000061801 -6.729 0.000001320 0.222533 6
> 55822 71035.304 -0.000041884 -6.729 0.000000778 0.208161 6
> 55822 71100.304 -0.000023847 -6.729 0.000000629 0.194717 6
> 55822 71166.303 -0.000003148 -6.595 0.000001515 0.188165 6
> 55822 71232.302 0.000006531 -6.595 0.000004666 0.176012 6
>
NetBSD-5, ntpd 4.2.6p3
My time sync has blipped twice each evening at times when
system load is high during log creation/rotation. Mostly
I don't notice. Currently I'm using a Sure-Electronics
but my Garmin 18x-LVC was the same. Blips are from < 15u
up to over 40u.
peerstats.20110918
ident mean rms max delay dist disp
127.127.20.2 -64.698 15.422 60.828 0.000 2.525 1.742
127.127.22.2 0.000 0.000 0.048 0.000 0.928 0.920
David
> Can anyone help??
>
> Thanks!
>
> Cheers,
> Miguel
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