Im running an intel atom also (old one, d945gclf2 board), and its only
doing ntp at the moment with a fairly minimal 64bit ubuntu 12.10 server.
after 24 hours its now looking like this:
remote refid st t when poll reach delay offset
jitter
==============================================================================
+203.0.178.191 43.128.117.84 2 u 38 64 377 8.960 -11.714
0.169
*27.54.95.12 218.100.43.70 2 u 31 64 377 61.301 -1.256
0.246
-202.6.248.7 130.102.128.23 3 u 46 64 377 9.529 -0.273
0.160
-116.66.162.4 130.234.255.83 2 u 52 64 377 20.386 15.747
1.988
+121.0.0.41 204.152.184.72 2 u 59 64 377 25.295 -4.202
3.760
o127.127.20.0 .GPS. 0 l 1 8 377 0.000 -0.001
0.001
I've just tuned the gps so that its only outputing a single nmea
sentence (GPZDA) and increased the speed to 9600 and now its no longer
needing the fudge factor. Ultimately though, i'll want to try get it
running from a geode based machine (which has some seriously low specs,
but it'll be amusing to see how it performs).
Something else i've noticed as well when im watching it, when it adjusts
the system time it seems to impact the jitter calculation quite
considerably and with the other ntp servers in there, it doesnt always
seem to want to choose the gps as the absolute truth.
On 07/04/13 23:46, David Taylor wrote:
On 07/04/2013 11:14, Paul J R wrote:
Hi All,
I've got a SiRF star 3 GPS with a PPS line which im trying to get
running on a machine with ubuntu 12.10 and a serial port using the DCD
line for pps signalling.
[]
o127.127.20.0 .GPS. 0 l 4 8 377 0.000 -0.065
0.003
[]
Seems like a pretty decent little gps unit, assuming i've got it
functioning and configured correctly?
Just for comparison:
Intel Atom PC running FreeBSD 8.2 (Pixie):
o127.127.20.1 .PPS. offset/jitter -0.001 0.002
Two Raspberry Pis running Linux 3.2.27+
o127.127.22.0 .PPS. offset/jitter 0.002 0.002
o127.127.22.0 .PPS. offset/jitter 0.001 0.002
Raspberry Pi running Linux 3.36.11
o127.127.22.0 .PPS. offset/jitter 0.000 0.002
65 microseconds offset seems a little high to me, but the PCs I've
just quoted are all (mostly) /only/ serving NTP. I have been doing a
little installation work on Raspberry Pi #3 today, and it now has a
steady CPU and network I/O load. Its PPS was only configured
yesterday. Performance graphs are here:
http://www.satsignal.eu/mrtg/performance_ntp.php
I hope that helps your comparisons.
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