The Intel 8259 is a programmable interrupt controller.

Hardware interrupts can be controlled by the 8259 Programmable Interrupt Controller

Received when two devices were trying to use the same interrupt request (or IRQ) to signal an interrupt to the Programmable Interrupt Controller (PIC).

In computing, the term APIC stands for Advanced Programmable Interrupt Controller. It is a more advanced version of a programable interrupt controller, which uses interrupts onto CPU lines.

In an IBM PC or compatible computer, IRQ2 should not be used because it is internally cascaded from the second 8259 Programmable Interrupt Controller, so as to provide IRQ8 through IRQ15.