Date: Wed, 24 Dec 1997 11:55:49 -0600 (CST) From: Jim Bryant <jbryant@unix.tfs.net> To: freebsd-hackers@FreeBSD.ORG Subject: Re: procedure to adjust clock drift? Message-ID: <199712241755.LAA09424@unix.tfs.net>
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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+
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