Date: Sun, 7 Mar 1999 21:50:53 +0100 From: Pierre Beyssac <pb@fasterix.freenix.org> To: Poul-Henning Kamp <phk@critter.freebsd.dk>, Dave Mills <mills@huey.udel.edu> Cc: Ollivier Robert <roberto@keltia.freenix.fr>, current@FreeBSD.ORG, Harlan Stenn <Harlan.Stenn@pfcs.com>, "David L . Mills" <mills@udel.edu> Subject: Re: NTP nanokernel support (experimental) Message-ID: <19990307215053.A3517@fasterix.frmug.fr.net> In-Reply-To: <17044.920833790@critter.freebsd.dk>; from Poul-Henning Kamp on Sun, Mar 07, 1999 at 08:09:50PM %2B0100 References: <199903071351.aa20073@huey.udel.edu> <17044.920833790@critter.freebsd.dk>
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On Sun, Mar 07, 1999 at 08:09:50PM +0100, Poul-Henning Kamp wrote:
> I don't think Ollivier is doing PPP/hardpps() yet, at least I have not
> given him the semi-magic code needed for it :-)
>
> I wouldn't recommend trying it either, he is bound to have a >1
> msec jitter on the DCF77 waves at his place, and that is a lousy
> diet for hardpps().
I agree; jitter with a low-cost DCF77 receiver is even more than
that (5 to 10 ms). I tend to believe it's partly due to how the AM
signal is demodulated and not that much from the location (Paris
is not that far from Frankfurt after all). Maybe a lower jitter
could be obtained by averaging 10 or 100 samples, I suppose that's
how high-quality receivers work. This might be done in the ntpd
driver.
--
Pierre Beyssac pb@fasterix.frmug.org pb@fasterix.freenix.org
{Free,Net,Open}BSD, Linux : il y a moins bien, mais c'est plus cher
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