The I/O APIC consists of a set of 24 IRQ lines, a 24-entry Interrupt Redirection Table, programmable registers, and a message unit for sending and receiving APIC messages over the APIC bus.

• APIC由24条IRQ线、一个24条目的中断重定向表、可编程寄存器和一个通过APIC总线发送和接收APIC消息的消息单元组成。