linux-kernel - BIOS implementors disabling the LAPIC

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Message-ID: <46AEED9E.1050904@free.fr>
Date:	Tue, 31 Jul 2007 10:06:54 +0200
From:	John Sigler <linux.kernel@...e.fr>
To:	linux-kernel@...r.kernel.org
CC:	linux-rt-users <linux-rt-users@...r.kernel.org>
Subject: BIOS implementors disabling the LAPIC

I have several systems here where Linux tells me:
Local APIC disabled by BIOS -- you can enable it with "lapic"

As far as I understand, the Local APIC was integrated directly to the 
CPU 12-15 years ago. Why would a BIOS implementor choose to disable it?

(And what does it mean to "disable" the LAPIC?)

Note: the motherboard does not provide an IO-APIC.

I've ask the kernel to re-enable the LAPIC, and was able to use OProfile 
in hardware counter mode, i.e. it seems to work fine.

Regards.
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