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Date:      Mon, 7 Nov 2005 18:38:00 -0700 (MST)
From:      Vaibhave Agarwal <vaibhave@cs.utah.edu>
To:        John Baldwin <jhb@freebsd.org>
Cc:        freebsd-net@freebsd.org, freebsd-acpi@freebsd.org, current@freebsd.org, Nate Lawson <nate@root.org>
Subject:   Re: Freebsd 6.0 doesnt detect local APIC on a Pentium 3 machine
Message-ID:  <Pine.LNX.4.61.0511071830570.4600@trust.cs.utah.edu>
In-Reply-To: <200511071105.58729.jhb@freebsd.org>
References:  <20051027233636.GA39380@dmw.hopto.org> <Pine.LNX.4.61.0511061525330.16649@trust.cs.utah.edu> <436E874E.4010305@root.org> <200511071105.58729.jhb@freebsd.org>

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On Mon, 7 Nov 2005, John Baldwin wrote:

> And even then it can't be used for any device interrupts since there aren't 
> any I/O APICs.  On a UP machine without I/O APICs, it's actually probably 
> more optimal to just use irq0 and irq8 for clocks rather than the lapic timer 
> anyway.  The only real possible gain is the ability to use the profiling 
> interrupt from the local APIC.

I got access to the BIOS of the Pentium 3 machine I am using, but it has 
no option to enable/disable the local APIC.

Joseph Koshy is right, Linux enables the local APIC timer while booting 
up. I got the following in the bootup log of Linux 2.4 kernel on the same 
machine.

-------------------------
Local APIC disabled by BIOS -- reenabling.
Found and enabled local APIC!

Using local APIC timer interrupts. 
calibrating APIC timer ...
-------------------------

Though there is no I/O apic in the UP machines, but I only wanted to use 
local APIC timer in the lapic_timer_oneshot() mode to schedule few timers 
accurately.

thanks
vaibhave





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