[ntp:questions] Issues with w32tm on AD network

Martin Burnicki martin.burnicki at meinberg.de
Mon Feb 25 10:27:03 UTC 2008


Danny Mayer wrote:
> Jason Rabel wrote:
>>>>> Are there any GPS systems I could hook up to the Windows domain
>>>>> controller, and configure W32tm to use this?
>>>>>
>>>> Yes. Trimble, Palisade, NMEA, Jupiter, and HOPF (DCF77) Serial and PCI
>>>> are built for Windows. I cannot tell you much about them but the code
>>>> is built for them.
>>> Do these work with W32tm or NTPD for Windows?
>> 
>> I didn't think (the Meinberg build of) NTPD for windows supported any of
>> the refclocks? Or maybe they support the refclocks but no PPSAPI?
> 
> I don't think that Meinberg touches the config.h file when creating
> their builds. The refclocks that are to be supported are defined there.

Right. The config.h file is left untouched, so whatever is included by the
source code distribution is included by the binaries.

However, I don't know how the PPS API should be supported under Windows,
except that the Windows port would come with an own kernel driver which
evaluated a PPS input signal. 

The remaining question is whether it would make much sense at all to write a
such a driver since the resolution of the Windows clock is limited to ~16
milliseconds (1 ms under Vista, AFAIK).

We have sometimes requests from customers who think they can just install a
GPS PCI card in their Windows machine so their applications will get the
Windows system time wit better than 1 microsecond accuracy.

However, though some of the Windows API calls provide a resolution of 100
nanoseconds those API calls return exactly the same time stamps betwween 2
timer ticks, and then the returned time steps by the amount of the timer
tick interval.

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany




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