IRQ (Interrupt Request)
These are the hardware lines over which devices can send signals to get the attention of the processor; in other word the controlling the flow of communication is called interruption. Each device must have a unique IRQ line. Every CPU has a wire called the INT wire. If voltage is applied to this wire, the CPU suspends its current operations, save its status. And transfers to the interrupt handler (special routine), which contains the instructions for dealing with the device that cause of interrupt.To find out the IRQ values click start, program, Accessories, System Tools and System Information. Then extend the hardware resources to see the IRQ information. Following table shows the list of different IRQ,s and their availability to change.
| IRQ No | Available For Change | |
| IRQ 0 | System timer | No |
| IRQ 1 | Keyboard controller | No |
| IRQ 2/9 | Available | Yes |
| IRQ 3 | COM2, COM4 | Usually |
| IRQ 4 | COM1, COM3 | Usually |
| IRQ 5 | LPT2 | Usually |
| IRQ 6 | Floppy disk controller | No |
| IRQ 7 | LPT1 | Usually |
| IRQ 8 | Real-time clock | No |
| IRQ 10 | Available | Yes |
| IRQ 11 | SCSI/available | Yes |
| IRQ 12 | Available | Yes |
| IRQ 13 | Math coprocessor | Yes If there is no math coprocessor |
| IRQ 14 | Primary IDE controller | No |
| IRQ 15 | Secondary IDE controller | Usually |
