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APIC(4)			 BSD Kernel Interfaces Manual		       APIC(4)

     apic -- Advanced Programmable Interrupt Controller	(APIC) driver

     This driver is a mandatory	part of	amd64 kernel.  To compile this driver
     into i386 or pc98 kernel, place the following line	in your	kernel config-
     uration file:

	   device apic

     The following tunable is settable from the	loader(8):

     controls event timers functionality support. Setting to 0,	disables it.
     Default value is 1.

     Set this to 1 to disable APIC support, falling back to the	legacy PIC.

     There are two components in the Intel APIC	system,	the local APIC (LAPIC)
     and the I/O APIC.	There is one local APIC	in each	CPU in the system.
     There is typically	one I/O	APIC for each peripheral bus in	the system.

     Local APICs manage	all external interrupts	for a specific processor.  In
     addition, they are	able to	accept and generate inter-processor interrupts

     I/O APICs contain a redirection table, which is used to route the inter-
     rupts they	receive	from peripheral	buses to one or	more local APICs.

     Each local	APIC includes one 32-bit programmable timer.  This driver uses
     them to supply kernel with	one event timer	named "LAPIC".	Event timer
     provided by the driver supports both one-shot an periodic modes.  Because
     of	local APIC nature it is	per-CPU.  The timer frequency is not reported
     by	the platform and so automatically measured by the driver on the	first
     use.  Depending on	CPU model this timer may stop in C3 and	deeper CPU
     sleep states.  Driver automatically adjusts event timer priority and re-
     ports it to prevent entering dangerous sleep states when it is used.

     atrtc(4), attimer(4), eventtimers(4), hpet(4)

BSD			       December	20, 2011			   BSD


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