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Re: Time of day clock runs at twice the speed on (old) laptop

On Mon, 24 Nov 2008, Jared D. McNeill wrote:

Hi Magnus --

If you run the following command as root:

  # sysctl -w kern.timecounter.hardware=i8254

Does the problem go away?


# date ; sleep 10 ; date
Mon Nov 24 14:41:07 CET 2008
Mon Nov 24 14:41:27 CET 2008
# sysctl -w kern.timecounter.hardware=i8254
kern.timecounter.hardware: ACPI-Safe -> i8254
# date ; sleep 10 ; date
Mon Nov 24 14:42:05 CET 2008
Mon Nov 24 14:42:15 CET 2008

Everything else seems to work as well. What are the relevant options if I want to make this permanent in a custom kernel? (short of disabling ACPI entirely)

On Mon, 24 Nov 2008, Andrew Doran wrote:

FWIW, x86 timer calibration is unreliable in 4.0. It's fixed in -current,
which may matter here.

I'll try a recent snapshot and get back to you with the results. I realize that there is probably something wrong with the hardware here, but at least it might be interesting to know how the kernel would handle that case (I guess).


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