Solution:

The definition of the IRQ and Address for COM ports are fixed on PCM-5862. COM1 3F8-3FF IRQ4 COM2 2F8-2FF IRQ3 COM3 3E8-3EF IRQ10 COM4 2E8-2EF IRQ5 The CMOS configuration provides a phycal swap function for two pares: Port 1,2 swap COM1,2 and Port 3,4 swap COM 3,4. As you swap ports, the IRQ follows is address. For example if I swap COM3 and COM4 then my configuration becomes: Port 4 = COM3 3E8-3EF IRQ10 Port 3 = COM4 2E8-2EF IRQ5 *** If you need to swap the IRQ definition only of COM3 and COM4 (Address remain unchanged), Please swap hardware jumper of J8 and J9. Now this jumper is only with 2 pins so rework these two jumper is necessary. After your change J8 to 2-3 and J8 to 1-2, your hard ware configuration will be: COM1 3F8-3FF IRQ4 COM2 2F8-2FF IRQ3 COM3 3E8-3EF IRQ5 COM4 2E8-2EF IRQ10 But note that CMOS will still show that 3E8 is still IRQ10 and 2E8 is still IRQ 5. In fact the IRQ is already swaped.