text: Q:
  
  Does the 25-pin IBM PS/1 serial port connector contain two serial ports?
  
  I got my hands on an IBM PS/1 computer and it provides a 25-pin serial port connector. Whith the help of an adapter I can get a 9-pin serial port on COM1 and transfer data that way. I would like to know wether the PS/1 implements a secondary COM port on the 25-pin connector or if it is left unconnected.
  
  A:
  
  According to the IBM PS/1 Technical Reference Manual, the pin assignment of the serial port is:
  
  So to answer your question: no, there is neither a second port nor a secondary channel for the first port. All the secondary lines are not connected.
  
  A:
  
  DB25 in its very early stage provided for a secondary port on the same connector (using pins 12,13,14,16,19).
  Since then, those secondary and other additional signals became obsolete and even DB25 ports only use up to 9 signals - same as on in DB9 connector.
  It is possible that your motherboard provides another port and you would need to provide a cable for it, or you can install a PCI or ISA card with additional ports.
  The easiest way to verify would be to check if a system sees any port other than COM0 (or ttyS0), if it does - short pins 14 with 16 and see if you get echo of signals sent to that port.
  OR - check in the manual for your exact motherboard - it will give you definite answer.
  
  