Editing Intel 8259 (section)

{{more footnotes needed|date=September 2013}}
{{Use dmy dates|date=April 2024}}
[[File:Intel 8259A IRQ chip.JPG|thumb|Closeup of an Intel 8259A IRQ chip from a [[IBM Personal Computer XT|PC XT]].]]
[[Image:Intel 8259.svg|thumb|Pinout]]
The '''Intel 8259''' is a [[programmable interrupt controller]] (PIC) designed for the [[Intel 8085]] and [[Intel 8086|8086]] microprocessors. The initial part was 8259, a later A suffix version was upward compatible and usable with the 8086 or [[Intel 8088|8088]] processor. The 8259 combines multiple [[interrupt]] input sources into a single interrupt output to the host microprocessor, extending the interrupt levels available in a system beyond the one or two levels found on the processor chip. The 8259A was the interrupt controller for the [[ISA bus]] in the original [[IBM PC]] and [[IBM PC AT]].

The 8259 was introduced as part of Intel's [[Intel 8085#MCS-85 family|MCS 85]] family in 1976. The 8259A was included in the original PC introduced in 1981 and maintained by the [[PC/XT]] when introduced in 1983. A second 8259A was added with the introduction of the [[PC/AT]]. The 8259 has coexisted with the [[Intel APIC Architecture]] since its introduction in [[symmetric multiprocessor]] PCs. Modern PCs have begun to phase out the 8259A in favor of the Intel APIC Architecture. However, while not anymore a separate chip, the 8259A interface is still provided by the [[Platform Controller Hub]] or [[southbridge (computing)|southbridge]] on modern [[x86]] motherboards.<ref>{{Cite web|url=https://www.datasheetcatalog.com/info_redirect/datasheet/Intel/mXvqwzr.pdf.shtml|title=Intel datasheet |website=www.datasheetcatalog.com|access-date=30 April 2024}}</ref>