Legacy Ports
  
  Point to point - connects a single device to the controller interface.

  Primary address implemented by choice of port by controller.
    If secondary addressing scheme implemented on device,
      this address is often passed as data
      sometimes combined with control signals.

  Often dedicated purpose - designed for specific 'device'.
    Centronics printer, PS2 (mouse/keyboard)

    Minimal controls and protocol. - Only those for specific devices.

    May provide only uni-directional data movement.
      Early parallel printer ports - data just flowed from PC to printer.

  Historical

    Keyboard/Mouse  * largely replaced by USB. External.
      XT/AT Keyboard port.

      PS/2 - keyboard/mouse ports.
    


    Printer port
    
      8-bit unidirectional data.

      Memory mapped control I/O.

  
    AGP - Advanced Graphics Port - (2004) Video cards. Internal.
      Single point to point interface  between video card and processor.

      Modified (supercharged) PCI interface.

      Video card also connected to an external video port such as VGA or DVI.


    VGA - Video Graphics Adapter
      
      External.

      Analog.  


Modern implementation - also see networked below. 
  Often implements packetization and virtual bus implementation.
  May support routing - so not true single point to point connection.
 
  
    Serial ATA (drive interface)
    Implements Parallel ATA over serial communication. 
    One one drive per connection. 
    Controller capable of interfacing with multiple drives
      at very high speeds.

  
    PCI Express - Peripheral Interconnect Interface over serial communication.
      Multiple independent serial lanes available.
    Packet driven communication.
    One 'device' per connection.
    Controller capable of interfacing with multiple drives
      at very high speeds.

    DVI External.
    

    HDMI External.
    
    

    Display-Port - video. External.
    
 
    Mini Display-port External.
    
      Uses packetized information - allowing expansion of protocol at
        software level.

      Supports daisy-chaining of monitors.

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