Asus P4B266-C - Manual (Page 94)

4-32 Chapter 4: BIOS Setup
Interrupt Mode [APIC]
The Advanced Programmable Interrupt Controller (APIC) setting allows
you to distribute interrupt routings other than the 16 IRQs. The
Programmable Interrupt Controller (PIC) setting allows you to use the 16
IRQs only. Configuration options: [PIC] [APIC]