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 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)

Debian                                            June 19, 2020                                          APIC(4)