[LinuxPPS] PC Clock Offset

[Bernhard Schiffner]

On Friday 12 June 2009 00:47:07 Andrew Hills wrote:
...
>
> Can I assume the "DELAY 25.0 ns" line in my ntp.oncore.0 configuration
> file compensates for the cable delay? How could I go about measuring and
> compensating for the PPS interrupt handler latency?
>
> --Andrew Hills

Yes you can assume so.

A useful measurement is only possible in your host can generate an output 
signal.
(I have no idea how to perform such a check in a good way. If you don't 
measure an interupt line directly there will alwayse be delays by software.)

After such a hyptheticval measurement you assume that "somewhere in the 
middle" is the time of interest.

ntpd is by no means designed to enable measurements or verification. It only 
states about some computations.

You can estimate some _improvements_ of latency if you change something in 
software. But it's (with x86 architecture) quasi impossible to "align" hard- 
and software.

 :-(

Bernhard