[ntp:questions] Linux 11-minute mode (RTC update)

Unruh unruh-spam at physics.ubc.ca
Sat Apr 5 18:31:11 UTC 2008

Serge Bets <serge.bets at NOSPAM.laposte.invalid> writes:

>Hello Bill,

> On Friday, April 4, 2008 at 16:16:22 +0000, Bill Unruh wrote:

>> what you really want is the drift rate of the crystal when the
>> computer is shut off ( ie cooling or cold)

>That's very true for workstations halted each evening; much less for
>Spoon's 24/7 servers.

>> all you can measure is the drift rate when it is on (warm and
>> constant)

>One can easely measure the power-off RTC drift rate at room temperature:
>Just shutdown the machine during some hours between two well synced
>invocations of hwclock --systohc, and then:

>| $ awk '{printf "%+.3f ppm", -$1 / 0.0864; exit}' /etc/adjtime
>| +12.345 ppm

Sure, and you can also do it with a lab full of equipment and a good time
source. That is not the question under discussion. The question is whether
or not the drift compensation in hwclock is worthwhile. I would say a bit,
but much less than you might think.

>Serge point Bets arobase laposte point net

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