| The number of serial ports that are identified by the operating system is less than the number of installed serial ports. | - Make sure that:
- Each port is assigned a unique address in the Setup utility and none of the serial ports is disabled.
 - The serial-port adapter (if one is present) is seated correctly.
 
  - Reseat the serial port adapter.
 - Replace the serial port adapter.
 
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| A serial device does not work. | - Make sure that:
- The device is compatible with the server.
 - The serial port is enabled and is assigned a unique address.
 - The device is connected to the correct connector (see System-board internal connectors).
 
  - Reseat the following components:
- Failing serial device
 - Serial cable
 
  - Replace the components listed in step 2 one at a time, in the order shown, restarting the server each time.
 - (Trained technician only) Replace the system board.
 
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