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APIC(4)		       FreeBSD Kernel Interfaces Manual		       APIC(4)

NAME
     apic -- Advanced Programmable Interrupt Controller	(APIC) driver

SYNOPSIS
     This driver is a mandatory	part of	amd64 kernel.  To compile this driver
     into i386 kernel, place the following line	in your	kernel configuration
     file:

	   device apic

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

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

     hint.apic.X.disabled
     Set this to 1 to disable APIC support, falling back to the	legacy PIC.

DESCRIPTION
     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
     (IPIs).

     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 and periodic	modes.	Be-
     cause of local APIC nature	it is per-CPU.	The timer frequency is not re-
     ported 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
     reports it	to prevent entering dangerous sleep states when	it is used.

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

FreeBSD	13.0			 June 19, 2020			  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO

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