| IRQ | Description | Used | Handled By |
|---|---|---|---|
| 0 | Timer Click | Yes | Default Handles |
| 1 | Keyboard | Yes | Default Handles |
| 2 | Second 8259A | Yes | BIOS |
| 3 | COM2 or COM4 | COM2 | BIOS |
| 4 | COM1 or COM3 | COM1 | BIOS |
| 5 | LPT2 or Sound Card (If present) | Yes | BIOS |
| 6 | Floppy Disk | Yes | Default Handlers |
| 7 | LPT1 | Yes | System Area |
| 8 | Real-Time Clock | Yes | Default Handlers |
| 9 | Redirected IRQ2 | Yes | BIOS |
| 10 | Sound Card (If present) | Yes | BIOS |
| 11 | (Reserved) | Free *1 | BIOS |
| 12 | PS/2 Mouse | Yes | Default Handles |
| 13 | Math Co-processor (If present) | Yes | BIOS |
| 14 | Fixed Disk | Yes | Default Handlers |
| 15 | Secondary Fixed Disk (If present) | Free *2 | Default Handlers |
*1 If a PBTV4 card is installed then IRQ 11 is used. *2 If an IDE CD-ROM is used then IRQ 15 is used.