Hello all,
My name is Ron Frazier and I'm a newbie to the list. I have several
computers that dual boot between Windows and Ubuntu. I've been using
NTP on Linux for a few years with its essentially default configuration
and a few NIST servers. I recently got interested in more accurate time
keeping after getting an "atomic" watch and a couple of "atomic" wall
clocks that listen to the WWVB time broadcast from Colorado in the US.
These, if they're up to specs, should always be accurate to 500 ms if
they're refreshed every day. I decided I wanted the same thing or
better for my PC's. Little did I know how hard that was. After some
research, I modified the ntp.conf files on the Linux side of my dual
boot fence to add some selected stratum 2 servers and some NTP pool
servers and tweak the polling intervals a bit. The NTP seems to be
keeping my Linux machines (when they're booted that way) accurate to
about 50 ms, which is OK. After much research, I decided to install the
Meinburg NTP server and monitor on my Windows machines. With a similar
ntp.conf, I can maintain accuracy in Windows of about 125 ms, which is
JUST OK. Sometimes it's better, but that's where the peaks on the graph
are. I could accept 500 ms, just like the radio clocks, but I don't
really want to.
At this point, I got interested in using GPS and setting up a local time
server. I'm not going to post all the details here at the moment, but I
have successfully configured a GlobalSat BU-353 USB GPS receiver on one
machine and am testing it. It is working nicely, and I believe almost
up to its maximum capabilities. I am consistently getting offset
accuracy of computer clock versus GPS of 15 ms with periodic spikes to
25 ms and jitter averaging around 3 ms. I'm looking into switching to
PPS, but that's another story. I have been exchanging a number of
emails with David J Taylor ( ref
http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html ) and asking
him questions about how to do all this and getting good answers. I hope
to edit those dialogs and post them either here or on his website or
both for everyone's benefit. (All total, they're pretty long. I'm not
sure what the etiquette is here about posting long messages.)
In any case, I have a very specific question today, mainly targeted
toward Dave Hart, but anyone can comment.
I updated the key NTP programs and am using NTP version
ntp-4.2.7p249-win-x86-bin from Dave Hart's website in my Windows system.
The NTPD service always starts out at RealTime priority. I believe,
based on some loopstats files, that using RealTime priority creates
periodic spikes where the offset upwards of 35 ms or so. Also, the
graph appears to have random jerks in it. When I manually switch to
Above Normal priority using task manager, my offset excursions tend to
stay within 15 ms and the graph is smoother. I don't have enough data
yet to prove my suspicions, but, I've set other programs to RealTime
priority before and found that it destabilized the system.
So, the question is, how do I force this process to always start at the
priority that I want, rather than having to change it each time in Task
Manager?
I'd like to know other people's opinion on this matter.
Any help is greatly appreciated and thanks in advance.
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
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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