STANDARD IRQ SETTINGS
IRQ Setting	Computer with an 80486 processor (or higher)	IRQ Setting	Computer with an 80486 processor (or higher)
0	SYSTEM TIMER    (Will not change)	7	LPT1, OLD, SB     (Will not change)
1	KEYBOARD     (Will not change)	8	Real time clock
2	Cascade to 9 (also secondary IRQ)	9	Cascasde 2 (unassigned)
3	COM 2, COM 4, NIC	10	Primary SCSI controller
4	COM1, COM3	11	Secondary SCSI controller
5	LPT2, NIC, SOUND CARD (Variable)	12	PS/2 Mouse
6	FLOPPY      (Will not change)	13	Unassigned
		14	Primary Hard Drive controller
		15	Unassigned
IRQ Settings 2 and 9 are left open, you cannot use both at the same time, although.
The Pecking Order if 0, 1, 2, 3, . . . . .  Etc.