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Vol. 3 8-31
MULTIPLE-PROCESSOR MANAGEMENT
mode address space (1-MByte space). For example, a vector of 0BDH specifies a
start-up memory address of 000BD000H.
11. Enables the local APIC by setting bit 8 of the APIC spurious vector register (SVR).
MOV ESI, SVR; Address of SVR
MOV EAX, [ESI];
OR EAX, APIC_ENABLED; Set bit 8 to enable (0 on reset)
MOV [ESI], EAX;
12. Sets up the LVT error handling entry by establishing an 8-bit vector for the APIC
error handler.
MOV ESI, LVT3;
MOV EAX, [ESI];
AND EAX, FFFFFF00H; Clear out previous vector.
OR EAX, 000000xxH; xx is the 8-bit vector the APIC error handler.
MOV [ESI], EAX;
13. Initializes the Lock Semaphore variable VACANT to 00H. The APs use this
semaphore to determine the order in which they execute BIOS AP initialization
code.
14. Performs the following operation to set up the BSP to detect the presence of APs
in the system and the number of processors:
— Sets the value of the COUNT variable to 1.
— Starts a timer (set for an approximate interval of 100 milliseconds). In the AP
BIOS initialization code, the AP will increment the COUNT variable to indicate
its presence. When the timer expires, the BSP checks the value of the COUNT
variable. If the timer expires and the COUNT variable has not been incre
-
mented, no APs are present or some error has occurred.
15. Broadcasts an INIT-SIPI-SIPI IPI sequence to the APs to wake them up and
initialize them:
MOV ESI, ICR_LOW; Load address of ICR low dword into ESI.
MOV EAX, 000C4500H; Load ICR encoding for broadcast INIT IPI
; to all APs into EAX.
MOV [ESI], EAX; Broadcast INIT IPI to all APs
; 10-millisecond delay loop.
MOV EAX, 000C46XXH; Load ICR encoding for broadcast SIPI IP
; to all APs into EAX, where xx is the vector computed in step 10.
MOV [ESI], EAX; Broadcast SIPI IPI to all APs
; 200-microsecond delay loop
MOV [ESI], EAX; Broadcast second SIPI IPI to all APs
; 200-microsecond delay loop
Step 15: