[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.


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?




(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
reply and have not heard from me in 1 - 2 weeks, send your message again.)

Ron Frazier
timekeepingdude AT c3energy.com

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