[ntp:questions] ntpd on embedded risc

Christopher Mire cnm3332 at gmail.com
Tue Feb 17 04:17:44 UTC 2009


I have a small embedded linux machine. Moxa UC-7112 Plus that I want to
use as NTP server. http://www.moxa.com/product/UC-7110-LX.htm
Its has MOXA ART ARM9 32-bit 192 MHz processor CPU.

Here are statistics I collected after using it a bit.  This is using gpsd
2.33 to collect NMEA, PPS.


     remote           refid      st t when poll reach   delay   offset
jitter
==============================================================================
+SHM(0)          .NMEA.           0 l    8   16  377    0.000  -21.691
7.812
*SHM(1)          .PPS.            0 l    1   16  377    0.000  -17.105
7.81

ntpq> cv
status=0101 clk_noreply, last_clk_noreply,
device="SHM/Shared memory interface", timecode=, poll=54, noreply=78,
badformat=0, baddata=0, fudgetime1=0.000, stratum=0, refid=PPS, flags=0
ntpq> rv
status=09e4 leap_none, sync_telephone, 14 events, event_peer/strat_chg,
version="ntpd 4.1.1 at 1.786 Tue Sep 11 19:14:27 CDT 2007 (1)",
processor="armv4tl", system="Linux2.6.9-uc0", leap=00, stratum=1,
precision=-7, rootdelay=0.000, rootdispersion=32.592, peer=4253,
refid=PPS, reftime=cd44982f.b9359791  Tue, Feb 17 2009  9:58:07.723,
poll=4, clock=cd449838.649a9973  Tue, Feb 17 2009  9:58:16.392, state=4,
offset=-13.494, frequency=142.853, jitter=7.908, stability=4.197

root at Moxa:~# cat /proc/cpuinfo
Processor    : ARM922Tid(wb) rev 1 (v4l)
BogoMIPS    : 76.59
Features    : swp half thumb
CPU implementer    : 0x66
CPU architecture: 4
CPU variant    : 0x0
CPU part    : 0x526
CPU revision    : 1
Cache type    : VIVT write-back
Cache clean    : cp15 c7 ops
Cache lockdown    : format B
Cache format    : Harvard
I size        : 16384
I assoc        : 2
I line length    : 16
I sets        : 512
D size        : 16384
D assoc        : 2
D line length    : 16
D sets        : 512

Some gpsd messages in case :
gpsd: <= GPS: $GPZDA,020012.000,17,02,2009,,*58
gpsd: carrier-detect on /dev/ttyM1 changed to 0
gpsd: carrier-detect on /dev/ttyM1 changed to 1
gpsd: ntpshm_pps: precision -6

ntp.conf
server 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 time1 0.411 refid NMEA
server 127.127.28.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.1 refid PPS

I am curious if the platform is the limitation, or if there are things that
can be done to make this work well as a NTP server, because now the accuracy
is unacceptable.  Ideas?



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