Interrupt Requests (IRQ)

INTERRUPT REQUESTS (IRQ) are physical connections between external hardware devices and the interrupt controllers. When a device such as a floppy drive controller or printer requires the attention of the CPU, an IRQ line is used to get the attention of the system to perform a task. On AT based systems, 16 IRQ lines are numbered IRQ0 through IRQ15. IRQ lines must only be used by a single adapter in the ISA bus systems. On PCI bus systems, adapters can share interrupts.