The interrupt request registers are used to handle interrupts coming from different internal and external devices. Multiple PCI devices can share an IRQ but multiple ISA devices cannot support multiple devices. The IRQs are numbered 0 to 15.
Some of the IRQ numbers are:
- IRQ - Assignment
- IRQ 0 - System Timer
- IRQ 1 - Keyboard
- IRQ 2 - Programmable Interrupt Controller; gateway to IRQs 9 - 15.
- IRQ 3 - COM2 (ttyb) I/O Base 2F8h (usually a ISA modem)
- IRQ 4 - COM1 (ttya) I/O Base 3F8h (usually a serial mouse)
- IRQ 5 - Usually a secondary printer, NIC, or sound card
- IRQ 6 - Diskette Controller
- IRQ 7 - Parallel Printer; sometimes used for a sound card
- IRQ 8 - CMOS Real-Time Clock
- IRQ 9 - Sometimes used for a sound or network card
- IRQ 10 - No assingment
- IRQ 11 - Sometimes used for PCI Video
- IRQ 12 - PS/2-style Mouse
- IRQ 13 - Math Coprocessor Exception
- IRQ 14 - Primary ATAPI Disk controller
- IRQ 15 - Secondary ATAPI Disk controller
The IRQ number 10 has no assignment: Such IRQs are usually the target of various cards such as the scsi, sound and network cards. The IRQs form the backbone of a computer operating system. It is responsible for the maintaining the flow of processes.
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