IRQ
IRQ stands for interrupt request. IRQs are used by peripherals as a way to bring the processor into attention. In the early PC-architecture the chips 8259A and 8259B takes care of the requests and sends them to the processor in form of ordinary software interrupts.
In Pentium-class (and some 80486-class) computers the IRQs can be handled by the I/O APIC.
IRQs in the PC AT environment
- IRQ0 = 8253/8254 interval timer
- IRQ1 = keyboard
- IRQ2 = reserved for the 8259B
- IRQ3 = COM1 and COM3
- IRQ4 = COM2 and COM4
- IRQ5 = LPT
- IRQ6 = Floppy drives
- IRQ7 = LPT
- IRQ8 = Real-time clock (RTC)
- IRQ9 = Video card
- IRQ10 - 12 = reserved
- IRQ13 = Math coprocessor
- IRQ14 = Primary IDE drives
- IRQ15 = Secondary IDE drives
See also
