Date: Sun, 26 Nov 2017 10:27:45 -0700 From: Ian Lepore <ian@freebsd.org> To: Bruce Evans <brde@optusnet.com.au> Cc: svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r326095 - head/usr.sbin/bsdinstall/scripts Message-ID: <1511717265.23588.43.camel@freebsd.org> In-Reply-To: <20171125201623.J1236@besplex.bde.org> References: <201711231729.vANHTVmo092083@pdx.rh.CN85.dnsmgr.net> <F94B65A7-D2AA-47FB-90C4-439DDFDD1AC7@shxd.cx> <20171124201621.K980@besplex.bde.org> <1511539000.94268.17.camel@freebsd.org> <20171125201623.J1236@besplex.bde.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sat, 2017-11-25 at 22:09 +1100, Bruce Evans wrote: > On Fri, 24 Nov 2017, Ian Lepore wrote: > > [...] > > Is there any use for ntp as a client if you have an atomic clock? Just to > validate both it and ntpd? > > Bruce Ntpd treats the atomic clock as one of its peers... the clock emits a PPS pulse and serves as a refclock peer. There generally also needs to be a network peer, or another type of refclock such as a gps receiver, to tell ntpd how to number the seconds. Some atomic clocks are able to number the seconds as well (such as a Microsemi 5071a cesium), but that's not a feature that's used often in my experience. When the frequency output of the atomic clock directly drives the kernel timecounter (obviously using some custom hardware), ntpd isn't very good at being just a network protocol server. It really wants to steer the kernel clock based on phase/frequency measurements from some peer. There are dregs of old "LOCKCLOCK" support code in ntpd which is supposed to handle the "clock is externally steered" case, but when I tried to configure and build it to run that way last year, I had no success (which could be due to poor documentation and my misunderstanding of it, or could just be the support has bitrotted). -- Ian
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1511717265.23588.43.camel>