[ntp:questions] Sure serial - USB with PPS performs 16% better after Windows reboot

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Sun Mar 25 20:51:29 UTC 2012


Hi all,

I think I've discovered something very interesting.  Just by chance, I 
had to take the laptop computer to someone else's house the other day to 
do some work.  So, I shut it down and unplugged the GPS and left.  When 
I came back, I plugged the GPS back in and rebooted.  After a while, I 
checked my graphs.  I found peak offsets in the 800 us range rather than 
in the 1.2 ms range I had seen before.  I restarted NTPD and started 
another graph.  After a while,  saw the 1.2 ms offsets I had seen in the 
past.  Then, after forming a theory that the reboot may have some 
effect.  I rebooted again.  After letting the graph run a while, I was 
again seeing offsets in the 800 us range.  See the graph below.

http://dl.dropbox.com/u/9879631/2012-03-24-2327-loopstats-reboot-restart-reboot.png

There are three distinct sections.  First, is the beginning.  Here, as 
you can see, the peak offsets are approximately + .8 / - .6 ms.  Then, 
there is the middle.  As you can see, peak offsets are approximately + 
1.2 / - 1.2 ms.  Then, there is the end.  There are two subsections 
here.  In the first, the peak offsets are approximately + .8 / - .6 ms 
again.  In the second subsection, the peak offsets are approximately + 1 
/ - .7 ms.  I don't know why there is a variance between the 
subsections.  However, the beginning of the graph is a time just after a 
reboot, the middle is a time just after an NTPD restart, and the end is 
a time just after another reboot.

I can use the signal either way.  I just thought this was interesting.  
Anybody know what's going on?

Sincerely,

Ron


-- 

(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such.  I don't always see new messages very quickly.  If you need a
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Ron Frazier
timekeepingdude AT c3energy.com



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