[LinuxPPS] ntp-dev-4.2.5p237-RC does sync with PPS for me

[William S. Brasher]

On Wed, 28 Oct 2009, clemens at dwf.com wrote:

> 
> Other than the ppstest (which is good) and the ntpq which shows that you are
> not syncing to the PPS source (even tho it has lower jitter) Im not sure 
> what you are seeing dynamically.
> 
> In 2.6.31.x (and perhaps earlier) the variable 
> 
> 	#define SHIFT_PLL  4 has been set to 2
> 
> there was also an implication in some of the postings that with this change
> you should be able to run with Hz = 1000.
> 
> When I have tried this, my ntp wandered all over the place.  It could start 
> with
> an offset of 10ms and after a while be at 15s, all the time being the CHOSEN
> device.  Mumph.
> 
> As an additional experiment, could you check what HZ you have set in your 
> kernel,
> and set it back to 100 if it is not already there.  This will require a 
> mrproper
> recompile of the kernel since Hz is used everywhere.
> 
> Im not too sure if this is going to solve your problem, but it caused me a lot
> of grief.
> 
> -- 
>                                         Reg.Clemens
>                                         reg at dwf.com
> 
> 
> 

The latest ntpd still rejects PPS running with the current stable kernel.

Both 32 bit and 64 bit kernels are linux-2.6.31.5, are built with the 
latest LinuxPPS patches, and are running with HZ = 100.  I am running 
ntp-dev-4.2.5p238-RC on both, and both ntpd's reject PPS and refuse to 
sync with it.

Both boxes work with ntp-4.2.4p7, and the 64 bit machine works as well 
with ntp-4.2.4p7 with HZ set to 1000.


The offset is actually quite good considering the boxes are synced to an 
external machine and not PPS.
  

(64 bit machine)
server             remote           refid      st t when poll reach   delay   offset  jitter
============================================================================================
spectre.q.lan xGPS_NMEA(0)     .GPS.            0 l   11   16  377    0.000   -0.024   0.001
spectre.q.lan xPPS(0)          .PPS.            0 l    5   16  377    0.000   -0.024   0.001
spectre.q.lan *chronos         .PPS.            1 u   42   64  377    0.115   -0.020   0.006


server             remote           refid      st t when poll reach   delay   offset  jitter
============================================================================================
tara.q.lan    xGPS_NMEA(0)     .GPS.            0 l    6   16  377    0.000    0.015   0.003
tara.q.lan    xPPS(0)          .PPS.            0 l    2   16  377    0.000    0.015   0.003
tara.q.lan    *chronos         .PPS.            1 u   37   64  377    0.206    0.039   0.008