2.6.32.6 (baremetal) fails to shutdown Intel i7 860 with P55 chipset.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> > >  I have tried using different reboot=X kernel command line arguments, but none of them have correct the rebooting issue. In fact the system hangs the same way in all cases.
> > 
> > <scratches his head> That is most bizzare.
> > Can you try to get the latest linux kernel and see how it works?
> > 
> 
> Well its not the 'latest' linux kernel, but I installed 2.6.30-8-amd64 from http://packages.debian.org/lenny-backports/kernel/linux-image-2.6.30-bpo.2-amd64 and the reboot hangs the same way.

That is too old. Use the one from http://kernel.org/. You will have to
compile it.
> 
> That leads me to believe something in the mechanism of a system reboot has changed since 2.6.26-2-amd64.

Just to be clear, your problem is not related to Xen, as your problem
happen on bare-metal, so I am changing the title. 
.. snip..
> root@localhost:/usr/src# diff ./linux-2.6-2.6.26/arch/x86/kernel/reboot.c ./linux-2.6-xen/arch/x86/kernel/reboot.c > diff.out
> root@localhost:/usr/src# nano diff.out
> root@localhost:/usr/src# diff -y ./linux-2.6-2.6.26/arch/x86/kernel/reboot.c ./linux-2.6-xen/arch/x86/kernel/reboot.c > diff.out2

Yes. Thanks for the diffs. There is nothing in it that catches my eye
as: "This is it!"