Geir G wrote:
Hello,
We use NTP to time synchronize our Windows-based data
collection/gateway systems. We have been running our software along
with ntpd.exe successfully for several years. However, we are now
facing a problem which I need help to resolve. Please note that I don't
think there is anything wrong with ntpd.exe. I think I must ask our
sub-vendor(s) the correct critical questions, and hope someone can help
with formulating those questions.
Platform: Embedded hardware platform. Pentium III 700MHz CPU. Windows
XP Embedded (Service Pack 2 level).
NTP version: 4.2.0, downloaded from http://norloff.org/ntp/
The system clock is stable if we run NTP and our software in
configurations like we have used previously. However, we have started
utilizing a 3rd party software component (an OPC server) in some
configurations, and it is in these configurations we experience
problems with unstable system clocks.
I have tried to isolate the problem the following way:
1. I start NTP. The system clock is stable and ntpq output indicates
"everything's fine". NTP generates no entries in the event log after
startup.
2. I start the 3rd party OPC server. I run ntpq -p and see a steadily
increasing offset. It seems the OPC server influences the system clock
negatively, and NTP finally has to reset the clock (event log entries):
time reset +6.023474 s
frequency error 6476 PPM exceeds tolerance 500 PPM
NTP continues to reset the clock as long as the OPC server is running.
This happens with about 15 minute intervals.
3. I stop the 3rd party OPC server. After some time the system clock is
again stable and ntpq output indicates "everything's fine". NTP
generates no entries in the event log.
4. I start the 3rd party OPC server again. The result is as described
in step 2 above.
I can't find anything in the OPC server documentation that indicates
that it performs adjustments to the system clock.
Which questions should I ask the OPC server and/or embedded hardware
vendor? I am course also happy if someone has advise on further things
to be checked.
Thanks in advance.
Geir
It may not be relevant to your problem but it might help if you
explained, briefly, what an "OPC Server" is and does.
The symptoms strongly suggest that your OPC server is somehow blocking
clock interrupts or causing Windows to lose them.
You probably will need to talk to the vendor of your OPC server about
the problem. You may also need to get some help from Microsoft (lots of
luck on that one!!)
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