Why does the PenMount RS-232 controller fail to work on COM3, but works fine on COM1 and COM2?
Please check the following:
1. Does the IRQ / IO address of COM3 conflict with other ports ?
2. Does the COM port work correctly with other devices such as a serial mouse ?
3. Is the COM port already occupied by other devices ?
4. Most Linux systems have the wrong settings for COM3 and COM4 and user may need to perform the make kernel action again after changing settings. Please refer to other Linux documents for details.
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