Programmable interrupt controller: Difference between revisions

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A '''Programmable Interrupt Controller''' ('''PIC''') is a device which allows priority levels to be assigned to its interrupt outputs. When the device has multiple interrupt outputs to assert, it will assert them in the order of their relative priority. Common modes of a PIC include hard priorities, rotating priorities, and cascading priorites. PICs often allow the cascading of their outputs to inputs between each other.

A '''Programmable Interrupt Controller''' (or '''PIC''') is an [[Intel]] [[8259A]] chip that controls [[interrupt]]s.

Starting with the [[286]]-based AT, there are two PICs in a [[personal computer]], providing a total of 15 usable IRQs.

One of the best known PICs, the [[8259A]], was included in the [[x86]] PC. In modern times, this is not included as a seperate chip in an x86 PC. Rather, its functionality is included as part of the motherboard's southbridge chipset. In other cases, it has been completely replaced by the newer [[APIC|Advanced Interrupt Controllers]] which support many more interrupts and much more flexible priority schemas.

The PIC has been superseded by an [[IO-APIC | Advanced Programmable Interrupt Controller]] (APIC), or 82489DX chip, that is enhanced for [[multiprocessor|multiprocessing]].

==See also==