| Note: | The Bolded lines are usually free IRQs except when it is used by the indicated or added devices. |
| IRQ | Description | Used | Handled By |
|---|---|---|---|
| Timer Click | Yes | Default Handles | |
| Keyboard | Yes | Default Handles | |
| Second 8259A | Yes | BIOS | |
| COM2 or COM4 | COM2 | BIOS | |
| COM1 or COM3 | COM1 | BIOS | |
| LPT2 or Sound Card (If present) | Yes | BIOS | |
| Floppy Disk | Yes | Default Handlers | |
| LPT1 | Yes | System Area | |
| Real-Time Clock | Yes | Default Handlers | |
| Redirected IRQ2 | Yes | BIOS | |
| Sound Card (If present) | Yes | BIOS | |
| (Reserved) | Free *1 | BIOS | |
| PS/2 Mouse | Yes | Default Handles | |
| Math Co-processor (If present) | Yes | BIOS | |
| Fixed Disk | Yes | Default Handlers | |
| 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.