[ntp:questions] difference between M12 & M12T GPS receiver

Xuehuan Li libryant at hotmail.com
Mon Feb 2 02:41:24 UTC 2004


I found ntpd running with the Motorola GPS receiver had a bug. Compared to 
the internet time sever, the ntpd running with a M12T gives the same time, 
while the M12 will be ahead 1 second to it. The hardware platform is a 
Pentium MMX PC104 CPU card, OS is linux 2.4.20-NANO, software is ntp-4.2.0 
with enable_ONCORE option. I monitor the serial port of the GPS receiver, 
and the output time of the two cards are the same in the same time(according 
to the @@Ha message). the following text is the status of the two time 
server. the 'test' is using a M12T card, while the 192.168.2.6 is using a 
M12 card.

     remote           refid      st t when poll reach   delay   offset  
jitter
==============================================================================
*192.168.2.6     .GPS.            1 u    9   64  377    0.433  113.484  
10.090
+test            .GPS.            1 u   60   64  377    0.406  -894.14  
11.027

ntpq> rv 21908
status=9624 reach, conf, sel_sys.peer, 2 events, event_reach,
srcadr=192.168.2.6, srcport=123, dstadr=192.168.2.250, dstport=123,
leap=00, stratum=1, precision=-18, rootdelay=0.000,
rootdispersion=1.602, refid=GPS, reach=377, unreach=0, hmode=3, pmode=4,
hpoll=6, ppoll=6, flash=00 ok, keyid=0, offset=123.967, delay=0.423,
dispersion=0.943, jitter=10.483,
reftime=c3c83070.fdf7a4e7  Mon, Feb  2 2004 10:12:00.992,
org=c3c8307f.6afdfc19  Mon, Feb  2 2004 10:12:15.417,
rec=c3c8307f.4b4f82f5  Mon, Feb  2 2004 10:12:15.294,
xmt=c3c8307f.4b2bdc26  Mon, Feb  2 2004 10:12:15.293,
filtdelay=     0.42    0.43    0.41    0.42    3.18    0.54    0.41    1.89,
filtoffset=  123.97  113.48  103.39   92.92   83.42   70.39   56.57   36.06,
filtdisp=      0.01    0.99    1.93    2.89    3.87    4.86    5.80    6.76
ntpq> rv 21909
status=9424 reach, conf, sel_candidat, 2 events, event_reach,
srcadr=test, srcport=123, dstadr=192.168.2.250, dstport=123, leap=00,
stratum=1, precision=-19, rootdelay=0.000, rootdispersion=1.007,
refid=GPS, reach=377, unreach=0, hmode=3, pmode=4, hpoll=6, ppoll=6,
flash=00 ok, keyid=0, offset=-873.821, delay=0.430, dispersion=0.944,
jitter=10.110, reftime=c3c83083.1552c16d  Mon, Feb  2 2004 10:12:19.083,
org=c3c8308a.6ae53650  Mon, Feb  2 2004 10:12:26.417,
rec=c3c8308b.4aa60913  Mon, Feb  2 2004 10:12:27.291,
xmt=c3c8308b.4a81cb46  Mon, Feb  2 2004 10:12:27.291,
filtdelay=     0.43    0.43    0.41    0.45    1.53    0.43    0.45    0.42,
filtoffset= -873.82 -883.93 -894.14 -905.17 -916.80 -927.97 -941.63 -961.09,
filtdisp=      0.01    0.98    1.93    2.90    3.89    4.88    5.87    6.86

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