Intel MultiProcessor manual Example A-1. Programming Local Apic for Virtual Wire Mode

System BIOS Programming Guidelines

;-----------------------------------------------------------------------				;
; InitLocalAPIC( )				;
;-----------------------------------------------------------------------				;
;				;
;	Initialize the local APIC to virtual wire mode.			;
;				;
;-----------------------------------------------------------------------				;
SVR		equ	0FEE000F0H
LVT1		equ	0FEE00350H
LVT2		equ	0FEE00360H
APIC_ENABLED		equ	000000100H
	public	InitLocalAPIC
InitLocalAPIC		proc	near
	push	ds	; save regs used for APIC init
	push	es
	push	esi
	mov	al,080h	; ensure NMI disabled
	out	070h,al
	in	al,021h	; read primary imr
	push	ax	; save settings
	mov	al,0ffh	; mask all off
	out	021h,al
	in	al,0a1h	; read secondary imr
	push	ax	; save settings
	mov	al,0ffh	; mask all off
	out	0a1h,al
	extrn	pmode_on : near
	call	pmode_on	; switch into real big mode

;

;The APIC spurious interrupt must point to a vector whose lower

;nibble is 0F, that is 0xF, where x is 0 - F. Here we use Int 00FH,

;which handles spurious interrupts and supplies the necessary IRET.

;This vector is assumed to have already been initialized in memory.

;Enable the APIC via SVR and set the spurious interrupt to use Int 00F

mov esi,SVR

mov	eax,[esi]	; read SVR
and	eax,0FFFFFF0FH	; clear		spurious vector (use vector
			00FH)
or	eax,APIC_ENABLED	;	bit 8	= 1
mov	[esi],eax	;	write	SVR

;

;Program LVT1 as ExtInt, which delivers the signal to the INTR signal of all

;processors' cores listed in the destination as an interrupt that originated

;in an externally-connected interrupt controller.

;

Example A-1. Programming Local APIC for Virtual Wire Mode

Version 1.4 A-3