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 tunables are 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
     interrupts 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.
     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 reports it to prevent entering dangerous sleep states when
     it is used.

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

FreeBSD 13.1-RELEASE-p6          June 19, 2020         FreeBSD 13.1-RELEASE-p6