Interrupt Request (IRQ)

  • INTERRUPTS
    • An Interrupt Request (IRQ) is a signal sent to the CPU instructing it to suspend its current activity and handle some external event
      • External events can be keyboard inputs or mouse movements
    • Interrupts are labeled as numbers
      • Typically, interrupts go from 0 – 15
      • Newer systems sometimes have over 16 interrupts
    • The most common interrupts are:
      • [ 0 ] — System Timer — reserved for internal use
      • [ 1 ] — Keyboard — only keyboard use
      • [ 2 ] — Cascade for IRQs 8 – 15 — original systems only had 8.  IRQ 2 is used to manage 8 – 15
      • [ 3 ] — Second RS-232 serial port — may also be shared by a fourth RS-232 serial port
      • [ 4 ] — First RS-232 serial port — may also be shared by a third RS-232 serial port
      • [ 5 ] — Sound card or second parallel port
      • [ 6 ] — Floppy disk controller — reserved for first floppy disk controller
      • [ 7 ] — First parallel port
      • [ 8 ] — Real-time clock — reserved for system clock use only
      • [ 9 ] — Open
      • [ 10 ] — Open
      • [ 11 ] — Open
      • [ 12 ] — PS/2 Mouse
      • [ 13 ] — Math coprocessor — reserved for internal use
      • [ 14 ] — Primary ATA controller — traditionally for hard drives
      • [ 15 ] — Secondary ATA controller — more ATA devices
    • Recently, the use of Peripheral Component Interconnect (PCI) has made it easier to share interrupts
Scroll to top