Local APIC Added in the P54C

The P54C version of the Pentium® was the first IA32 processor to incorporate the Local APIC (Advanced Programmable Interrupt Controller; see Figure 20-7 on page 480) into the processor core. The Local APIC had the following features:

• Permits the currently executing program to send an Inter-Processor Interrupt (IPI) message to the Local APIC in another processor over the 3-wire APIC bus.

• Permits the processor core to receive an IPI from another processor over the 3-wire APIC bus.

• The Local APIC incorporates a programmable timer that can generate an interrupt when it expires or at regular intervals.

• Permits the currently-executing program to be interrupted upon the receipt of an interrupt message from the IO APIC module over the 3-wire APIC bus. The IO APIC is integrated into the chipset.

• Permits the currently executing program to be interrupted upon detection of an asserted level on the processor's LINT0 (Local Interrupt 0) input.

• Permits the currently executing program to be interrupted upon detection of an asserted level on the processor's LINT1 (Local Interrupt 1) input.

A detailed description of the APIC can be found in “The Local and IO APICs” on page 1497.