[ntp:questions] Re: Differences in behaviour of ntpd 4.1.1 and 4.2.0 on Windows XP

Terje Mathisen terje.mathisen at hda.hydro.com
Thu Nov 20 21:23:16 UTC 2003

David J Taylor wrote:
>>I am a little confused over the differences in behaviour of ntpd 4.1.1
>>and 4.2.0 on Windows XP.
>>I have an acutime 2000 connected to a PC running ntp.    I am
>>comparing the offset between the acutime pps output and the pc time as
>>shown by an oscilloscope with the offset as reported by "ntpq -c pe".
>>  With 4.2.0 the offset as reported by ntpq tends to zero as expected
>>but the oscilloscope shows an offset of anything up to 700
>>milliseconds (this offset value varies each time ntp is restarted).
>>With 4.1.1 the offset as reported by ntpq agrees with the oscilloscope
>>to within the millisecond.
> Is there any question of the edge polarity of the two versions being
> different?  I.e. is the pulse about 700ms wide and NTP is triggering off
> the wring edge?  I don't run a PPS source, just throwing in the
> suggestion....

Nice suggestion, the default polarity of PPS have been changed at least 
once during the ntpd development process.

If this have happened here, then a switch to the opposite edge would 
indeed fix the problem.


- <Terje.Mathisen at hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"

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