From owner-freebsd-hackers Wed Dec 24 09:56:18 1997 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.7/8.8.7) id JAA20705 for hackers-outgoing; Wed, 24 Dec 1997 09:56:18 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from unix.tfs.net (pm3-p31.tfs.net [206.154.183.223]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id JAA20660 for ; Wed, 24 Dec 1997 09:55:59 -0800 (PST) (envelope-from jbryant@unix.tfs.net) Received: (from jbryant@localhost) by unix.tfs.net (8.8.8/8.8.5) id LAA09424 for freebsd-hackers@freebsd.org; Wed, 24 Dec 1997 11:55:49 -0600 (CST) From: Jim Bryant Message-Id: <199712241755.LAA09424@unix.tfs.net> Subject: Re: procedure to adjust clock drift? To: freebsd-hackers@FreeBSD.ORG Date: Wed, 24 Dec 1997 11:55:49 -0600 (CST) Reply-to: jbryant@unix.tfs.net X-Windows: R00LZ!@# MS-Winbl0wz DR00LZ!@# X-Operating-System: FreeBSD 3.0-CURRENT #0: Mon Dec 1 15:51:40 CST 1997 X-Mailer: ELM [version 2.4ME+ PL31H (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk if you are adventurous, you can tweak the loading capacitor for the clock crystal.. to zero the clock to the design frequency. best way to do this is to get a frequency counter and monitor the output of the oscillator while tweaking the capacitor [the variable near the crystal]. if you don't have a counter, the next best way to do this is to try trial and error by ear using some known reference such as WWV. to get a properly adjusted oscillator, you can spend upwards of a month using the trial and error method, as only cumulative error will be noticable. use a counter if you can find one!B this can be alleviated by running xntpd or timed, which by getting the time from a stratum 1 timeserver at regular intervals can skew the clock via software to correct for the frequency error of the oscillator. In reply: > It was Warner Losh who wrote: > > In message <199712231738.JAA01502@rah.star-gate.com> Amancio Hasty writes: > > : Does anyone have a procedure to adjust the clock drift in a PC? > > If you think of hardware tuning the frequency: No, I don't know. > (It will depend e.g. on whether you have the machine running all > the time or just during the day (temperature).) > > > If you are happy with periodically synchronizing the clock to > some time standard: > > I wrote some time ago a driver which connects a cheap DCF clock > (german radio standard time signal (others should be easy to implement) > controlled, price at about 10-20 $) via a simple interface to my > (otherwise unused :-) game port (iX 11/1994p6). > > The kernel polls every 1/100 s the state and buffers it for a > user program to evaluate (which I run via cron twice a day). > In a network I use xntpd with the machine with the clock configured > as a stratum 1. > > The driver (including a plan for the interface) can be found at: > ftp://hadron.tp2.ruhr-uni-bochum.de/pub/DCF/DCF77-1.3-beta.tar.gz > > (the `beta' reflects the fact that the Readme is in German and it > needs some hand work to apply the patches to the kernel (no port)) > > A slightly different solution exists for the serial port with direct > interface to ntp (in iX 10/1994p154). > In this article the authors point to parse/util/dcfd.c in the > NTP-distribution. > > > Robert > > > > > ntp? > > > > It is already in the tree as xntpd and friends... > > > > Warner jim -- All opinions expressed are mine, if you | "I will not be pushed, stamped, think otherwise, then go jump into turbid | briefed, debriefed, indexed, or radioactive waters and yell WAHOO !!! | numbered!" - #1, "The Prisoner" ------------------------------------------------------------------------------ Inet: jbryant@tfs.net AX.25: kc5vdj@wv0t.#neks.ks.usa.noam grid: EM28pw voice: KC5VDJ - 6 & 2 Meters AM/FM/SSB, 70cm FM. http://www.tfs.net/~jbryant ------------------------------------------------------------------------------ HF/6M/2M: IC-706-MkII, 2M: HTX-212, 2M: HTX-202, 70cm: HTX-404, Packet: KPC-3+