> -----Original Message----- > From: Miroslav Lichvar [mailto:mlich...@redhat.com] > Sent: Wednesday, May 02, 2018 6:46 AM > To: Keller, Jacob E <jacob.e.kel...@intel.com> > Cc: Cliff Spradlin <thr...@google.com>; linuxptp-users@lists.sourceforge.net > Subject: Re: [Linuxptp-users] ptp4l and SyncE > > On Thu, Apr 26, 2018 at 06:24:39PM +0000, Keller, Jacob E wrote: > > In the case of two X550T cards, I would expect there to be *some* > > difference, > but if the clock sources are high quality it is possible they are close > enough that > we can't detect any difference in them? (though, changing frequency in on PHC > using the ptp API should not affect the other, unless something else is > connecting > them...) > > As expected, changing the PHC frequency on one card doesn't seem to > change the frequency on the other. > > I left them running for a couple of days, both frequencies set to 0 > with phc_ctl, and logged the offset measured by ptp4l using the NTPSHM > servo (i.e. not making any adjustments). The offset between them is > not exactly zero, but it's actually about 0.46 ppb. It seems to be the > same with both 1Gb and 10Gb link speeds. > > Here is a plot of the Allan deviation: > https://i.imgur.com/jp3ZE3Z.png > > Unless they have a hidden chip-scale atomic clock, I think they must > be synchronized to each other in some way. Maybe something was > implemented in preparation for SyncE support? > > -- > Miroslav Lichvar
Could be, I don't know enough about the clock setup in the X550T. Thanks, Jake ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
