APIC Advanced Programmable Interrupt Controller, a newer version of the original PC PIC (programmable interrupt controller). Most modern CPUs contain an on-chip APIC, called a local APIC. Many systems also contain an I/O APIC (input output APIC) as a separate chip which provides more than 16 IRQs. Windows 2000 and later use a different kernel if they detect an I/O APIC during installation. Therefore, an I/O APIC must not be removed after installation.