There is a bug in the BIOSes of some HP boxes with AMD Turions which
connects IO-APIC pins with ACPI thermal trip points in such a way that
if the state of the IO-APIC is not as expected by the (buggy) BIOS, the
thermal trip points are set to insanely low values (usually all of them
become 16 degrees Celsius).  As a result, thermal throttling kicks in
and knock the system down to its shoes.

Unfortunately some of the recent IO-APIC changes made the bug show up.
To prevent this from happening, blacklist machines that are known to be
affected (nx6115 and 6715b in this particular case).

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=11516 listed as
a regression from 2.6.26.

On my box it was caused by:

commit 691874fa
Author: Maciej W. Rozycki <macro@linux-mips.org>
Date:   Tue May 27 21:19:51 2008 +0100

    x86: I/O APIC: timer through 8259A second-chance
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

and the whole story is described in this (huge) thread:

    http://marc.info/?l=linux-kernel&m=121358440508410&w=4

Matthew Garrett told us about that happening on the nx6125:

    http://marc.info/?l=linux-kernel&m=121396307411930&w=4

and then Maciej analysed the breakage on the basis of a DSDT from the
nx6325:

    http://marc.info/?l=linux-kernel&m=121401068718826&w=4

As far as the Dmitry's and Jason's boxes are concerned, I recognized the
symptoms and asked them to verify that the blacklisting helped.

It appears that the buggy BIOS code has been copy-pasted to the entire
range of machines, for no good reason.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Tested-by: Jason Vas Dias <jason.vas.dias@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>