[time-nuts] pc clock crystal long term variations
attila at kinali.ch
Tue Aug 10 11:16:56 UTC 2010
On Sun, 08 Aug 2010 21:40:35 +0000
"Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:
> DEC used way better crystals than the average PC-HW producers, so
> I am not very surprised. Not sure if this was just general good
> engineering or a panicy reaction to all the trouble the alphas
> gave them.
> They had a few machines that could slot either x86 of alpha CPU
> boards, and they were built from very high quality parts.
This machine is a quite "cheap" dual P-II 266 system. No way to
fit in Alpha CPUs. Though, there were Alpha machines in the same
case. I guess they must have used very expensive crystals back
> >And why doesnt the
> >crystal relax back into it's old ppm value, but stays where it
> >is after a reboot/power cylce?
> You kernel tries to measure/estimate the crystal frequency at boot,
> it does not get the same value on every boot.
Do mean the BogoMIPS callculation of linux? I don't know of any
other timing dependend loop in there.
> Check your syslog/dmesg for the frequency estimate and you can see
> this clearly.
I will try to fit the BogoMIPS data over the ntp loopstats and see
what that yields.
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If you want to walk far, walk together.
-- African proverb
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