Solution:

WinNT can provide standard communication driver and sharing interrupt function, but the default setting of sharing interrupt is disabled. If you would like to use independent IRQ for each port, you just refer to the following steps to complete it: Step1: Please follow the below path and prepare to add a new port: [Start] => [Settings] => [Control Panel] => [Ports] Step2: Click [Add] and set proper I/O address and IRQ. Step3: Don't reboot right now if you want to add another port continuously. Step4: Repeat step2 to add other ports, just like the following: Ex: 741, 743, 745 Port 1 => COM3, I/O 3E8h, IRQ 5 Port 2 => COM4, I/O 2E8h, IRQ 7 Ex: 746+, 749, 840, 849 Port 1 => COM3, I/O 300h, IRQ 5 Port 2 => COM4, I/O 308h, IRQ 7 Port 3 => COM5, I/O 310h, IRQ 9 Port 4 => COM6, I/O 318h, IRQ 10 ... .. ... ... ... Note: Please make sure the hardware settings are the same with the software's, besides that, I/O address and IRQ don't conflict with other devices. Step5: Please restart WinNT to take new settings effect.