| Re: [chrony-dev] 1.24-pre1-- sudden change in rtc slope |
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On Mon, Dec 21, 2009 at 04:01:11PM -0800, Bill Unruh wrote:
> Actually the whole rtc philosophy is suspect. He tries to make
> an accurate measurement of the rate of the rtc, but of course with the machine
> switched off, the rtc is much colder than when on, and thus at a very
> different rate. I suspect that the rate following of the rtc in chrony is
> useful for rate corrections between turnons of the computer to no better than
> 10PPM.
I'd expect the chip isn't colder by more than 20 degrees when turned
off in usual desktop conditions, which should be less than 2 ppm.
Anyway, I'm trying on the HPET machine 10 times longer intervals
between rtc readings and it seems to be giving much better results.
-2.386137 1 -2.391095 -3.014 24 13 2400
-2.387779 1 -2.398386 -3.026 25 12 2400
-2.405598 1 -2.405603 -3.028 26 12 2400
-2.407479 1 -2.407806 -2.906 27 15 2400
-2.409800 1 -2.414456 -2.899 28 15 2400
-2.411616 1 -2.420868 -2.883 29 15 2400
-2.433798 1 -2.428422 -2.893 30 16 2400
-2.440425 1 -2.440334 -2.982 31 16 2400
The interval stays at the 2400 second maximum and no sample was
discarded yet. Maybe an rtc option similar to minpoll, maxpoll would
be a good idea?
--
Miroslav Lichvar
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