Solution:

I. CMOS Setting To set up Serial port please check the settinf in " Intergrated peripheral" of CMOS setting. Make sure your COM ports are configure with proper IRQ and IO address normally. COM1 IRQ4 Address: 3F8 COM2 IRQ3 Address: 2F8 You may double check the setting form system boot up configuration window. II. COM port function test guide A.How to setup serial port for Windows 95/NT? [ For Windows 95 ] 1. [Start] -> [Setup] -> [Control Panel] -> [Add New Hardware] 2. Click [Next], choose [N]ot to do auto search new hardware. 3. Click [Next], choose [Connection Port (COM & LPT)] Hardware Type. 4. Click [Next], select [Standard Connection Port Type] for manufacurer and [Communication Connection Port] for model. 5. Click [Next], then the default IRQ and IO Address will be shown. Click [Done]. Up to this point you have added a port to system without correct IRQ and IO settings. You can repeat step 1 to step 5 to add as many ports as you want (Max. 128 port). 6. [Control Panel] -> [System] -> [Device Manager] 7. Select your new COM?, then [Resource] 8. Select the ??? as [Basic Configure 8]. 9. Double click on IRQ to type in (select) the hardware IRQ, then [OK] 10. Double click on I/O rage to type in (select) the hardware I/O, then [OK]. Repeat step 6 to step 10 to setup each port correctly. 11. Click [OK] 12. Restart Windows 95 [ For Windows NT ] Similar to Windows 95. You add new serial port in the Control Panel. B.How to test serial port under DOS environment? We use COMTEST.EXE (as attached) under DOS environment,you may open the compressed file to get comtest program. 1.Run comtest.exe 2.CardType->PCL740. 3.Setup two serial port for port A and port B in "setting". 4.Choose the communication test way in "Diagnose",and there is the wiring diagram on right side of