PII SMP system hangs during boot with ACPI enabled

Nate Lawson nate at root.org
Mon Nov 24 13:49:09 PST 2003

On Mon, 24 Nov 2003, Poul-Henning Kamp wrote:
> In message <XFMail.20031124130939.jdp at polstra.com>, John Polstra writes:
> >On 24-Nov-2003 Nate Lawson wrote:
> >> It's a long shot, but what about setting kern.timecounter.hardware to
> >> i8254.  It appears your ACPI timer is bad.  The reason why I suggest this
> >> is that it seems like interrupts are being lost.
> >
> >I put kern.timecounter.hardware="i8254" into /boot/loader.conf, but
> >it didn't make any difference.  Are you sure it even works from
> >loader.conf?  From the sources it looks like this is a sysctl rather
> >than a tunable.  I could change it to a tunable, though, if you
> >think it's worthwhile.
> It would be rather complicated to make it a tunable.  Far easier to
> go into the ACPI timecounter and just give it a negative quality,
> that will disable it.
> I'm not sure why Nate think this will change anything with respect
> to interrupts, but I pressume he knows what he's talking about.

Some ACPI timecounters on old systems would hang on a read from the
register and so moving to i8254 would help if it was being used.  But
farther down, I see that he was already using TSC so it won't make a


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