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Diffstat (limited to 'sys-utils/hwclock.8.in')
| -rw-r--r-- | sys-utils/hwclock.8.in | 22 |
1 files changed, 0 insertions, 22 deletions
diff --git a/sys-utils/hwclock.8.in b/sys-utils/hwclock.8.in index 8cf86a362..79c79077d 100644 --- a/sys-utils/hwclock.8.in +++ b/sys-utils/hwclock.8.in @@ -938,28 +938,6 @@ Clock is corrected properly at startup. To check this, first make sure that the System Time is correct before shutdown and then use .BR \%sntp ", or " \%date\ \-Ins and a precision timepiece, immediately after startup. -.PP -Both clocks typically use a quartz crystal oscillator. Crystals are -used for reference oscillators in electronics because by most measures -they produce a very clean and stable sine wave. Their greatest -shortcoming is that they have a Positive Temperature Coefficient; -meaning that their frequency increases as the temperature increases and -vise versa. Therefore, both the Hardware and System Clock's drift rate -changes with intrinsic and extrinsic machine temperatures. These -characteristics will vary by machine depending upon its design. -.PP -Drift correction strategies are many, but as a general guide the goal -would be to find a longterm average. A year long average to take into -account seasonal ambient temperature shifts may be a good target period. -So perhaps the date-time advances a bit in the summer and declines a bit -in the winter, but at the end of a year it balances to zero. -.PP -If this is beginning to sound futile, it is not. Left on its own a -machine can lose 3 seconds per day or more. Accumulated drift over a -year may easily exceed half an hour. Using carefully crafted drift -corrections can make a significant improvement in a machine's ability to -keep reasonably good date-time. -. .SS LOCAL vs UTC Keeping the Hardware Clock in a local timescale causes inconsistent daylight saving time results: |