Parallel Ports - An introduction to parallel port technology


Credit for this information should go to Mark Clarkson (who says he hates parallel ports).

Current Technology

The parallel port on your PC today is a 1981 design, which runs at up to 150 Kb/sec. The maximum cable length is about 3 m.

New Technology

IEEE standard 1284 defines a newer, faster, and better parallel port, which will run at up to 4 Mb/sec. The good news is 1284 ports are backward-compatible with existing parallel ports. Even better news is that, for only the cost of a new cable, a 1284 parallel port can inject new life into your old printers. The maximum cable length will be about 10 m. Cables as well as ports are covered by the new standard.

Operating Modes

1284 ports come in 4 flavours.

    Name or                               peripherals  Major
    Acronym  Full name    Bidirectional?  per port?    usages
    -------  ---------    --------------  -----------  ------
    nibble                Yes
    byte                  Yes
    ECP      Enhanced     Yes                          host-to-
             Capabilites                               printer
    EPP      Enhanced     Yes             Yes          CD-ROMs,
             Parallel                                  hard disks


This simply means a 1284-compliant peripheral can talk to the host, eg to inform the host of its (the peripheral's) capabilities.

Related Articles

See my articles ``Serial Ports'' and ``SCSI Technology''.


'Pumping Up the Parallel Port', Byte, August 1994, p 118, by Mark Clarkson.


This article was written by Ron Savage in 1997. Email: