Default IRQ Settings
of a Computer
IRQ                                            Function                                  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                    If there is no math coprocessor
IRQ 14                                      Primary IDE Controller                             No
IRQ 15                                      Secondary IDE Controller                     Usually                               
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