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

Unruh unruh-spam at physics.ubc.ca
Wed Apr 9 18:18:15 UTC 2008

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

> On Monday, April 7, 2008 at 17:46:21 +0000, Unruh wrote:

>> if it is true that the hwclock routine sets/reads the system clock
>> better than does the kernel

>Well, neglecting drift, hwclock is already way more accurate than the
>kernel (several orders of magnitude better). And the kernel doesn't
>handle RTC drift. Check if you doubt.

>> that is up to  100PPM difference in the RTC between on and off.

>Aren't you drawing a general rule from a single out of bounds maybe
>dying example? I can provide a counter-example then. One Intel chipset
>RTC here drifts at:

>  +77.269 PPM powered-off during the night
>  +78.531 PPM runtime at day

>Which shows only 1.262 PPM variation between extreme conditions. That's
>the most stable I could find, of course. Don't draw conclusions from it.

But when one is advising someone, one must assume that they have at least
the typical if not the worst condition, unless one also tells one how to
check it. (How in the world did you the power off drift to 5 significant
figures? Even the poser on drift is not that accurate-- it wanders around
much more than 1PPB (part per billion)

>Serge point Bets arobase laposte point net

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