Network Time Foundation:
---+Manual Calibration without =NTP= This section describes how to calibrate the clock to an accuracy of order tenths of a second. This procedure was found useful when =ntpd= was used on a [[KnownHardwareIssues][variable speed processor]] and upset the drift correction. ---++ Linux The aim is to calibrate the kernel frequency adjustment variable(s) stored in =/etc/adjtime=. This following is a translation of [[https://www.linux-france.org/article/sys/heure/ch2.html#s-bref][Laurent Picouleau's page]]. Many thanks to Mike Cook for the above explanation and supplying this link. The following steps are to be done as =root=. * Day 1 * Set the CMOS clock to "approximately" UTC using the BIOS [[#FootNote1][(1)]]. * Install =hwclock= and =adjtimex= * Run =hwclock --set --date="MM/DD/YY hh:mm:00" --utc= [[#FootNote2][(2)]] =--debug= on the fourth beep (radio, I presume) [[#FootNote3][(3)]] * Day 2 * Run =hwclock --set --date="MM/DD/YY hh:mm:00" --utc --debug= * If the first value of the first line of =/etc/adjtime= is greater than 8 then * run =adjtimex -u -c= * record the suggested value for "tick" * run =adjtimex -u -t suggested_value= * Run =adjtimex -u -l=/var/log/clocks.log= * Day 7 * Run =adjtimex -u -l=/var/log/clocks.log= * Run =hwclock --set --date "MM/DD/YY hh:mm:00" --utc --debug= * Run =adjtimex -u -l=/var/log/clocks.log= * Run =hwclock --utc --hctosys= * Run =adjtimex -u -l=/var/log/clocks.log= * Run =adjtimex -u -c=22 -i=100= * Calculate the average of the 20 values given for "freq" * Run =adjtimex -u -f calculated_average= * Run =adjtimex -u -l=/var/log/clocks.log= Phew! Your clock system is now calibrated to your reference and will drift by about only one tenth of a second per day. *Footnotes:* #FootNote1 1. Or any other method #FootNote2 2. Note care the date format: month/day/year #FootNote3 3. Use local time, don't use GMT. -- Users.ParkerJones - 25 Nov 2004
This topic: Support
Topic revision: r1 - 2004-11-25 - 15:40:00 -
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