[ntp:questions] windows device manager and serialpps.sys

Dave Hart davehart at gmail.com
Wed Nov 30 14:51:23 UTC 2011

On Tue, Nov 29, 2011 at 14:54, Mark C. Stephens <marks at non-stop.com.au> wrote:
> I am running 4.2.7p98-o and I am uncertain whether or not PPS is working.

That's a relatively antique snapshot of ntp-dev.  At least with more
recent ntp-dev, if PPSAPI is enabled for NMEA using flag1 1 as you
have, the NMEA refclock driver will log an error message on startup if
PPSAPI is not working that mentions both PPSAPI and flag1 1.  See your
event log or a configured ntp.log.

There are less direct things you could try, like see if manually
lowering the ntpd process priority class from Realtime to Low then
throwing some work at the machine increases the offset ntpd reports
for the NMEA association.  If PPSAPI is working the timestamps are
snapped at serial port interrupt time and will not be affected by
additional ntpd scheduling latency.

Dave Hart

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