Please review this document fragment

Sanjeev Gupta ghane0 at
Mon Nov 25 23:15:30 UTC 2019

From: docs/driver_shm.adoc

Is the first paragraph still required, if it doesn't apply to current

And I cant parse the second paragraph, especially the first line.  What
should I use?  Not the ancient method, surely?

The _GPSD_ man page suggests setting minpoll and maxpoll to 4. That was
an attempt to reduce jitter. The SHM driver was fixed (ntp-4.2.5p138) to
collect data each second rather than once per polling interval so that
suggestion is no longer reasonable.

*Note:* The _GPSD_ client driver uses the _GPSD_ client
protocol to connect and talk to _GPSD_, but using the SHM driver is the
ancient way to have _GPSD_ talk to _ntpd_. There are some tricky points
when using the SHM interface to interface with _GPSD_, because _GPSD_
will use two SHM clocks, one for the serial data stream and one for the
PPS information when available. Receivers with a loose/sloppy timing
between PPS and serial data can easily cause trouble here because _ntpd_
has no way to join the two data streams and correlate the serial data
with the PPS events.
Sanjeev Gupta
+65 98551208
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the devel mailing list