The Disadvantages of Serial & Parallel Ports

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The transfer of data between the motherboard and computer is done using different types of cables through peripheral interfaces. As technology advances, older computer technologies like parallel and serial ports are replaced by newer forms like USB, or Universal Serial Bus, and IEEE 1394, or FireWire.

Parallel and standard serial ports come with several disadvantages when compared to newer technology.

Parallel Ports

In the early years of computing, the parallel port was the most used interface on a computer intended primarily for printers. It transferred data eight bits at a time over eight separate wires in a parallel cable through a DB-25 female connector, part of the D-subminiature style of connectors. Speed transmission of data was limited to 150 KBps (kilobits per second) and could only transmit within a range of ten feet. Standard parallel ports only transmitted data out unless it was a bidirectional port which most computers were equipped with from 1994 .

Serial Ports

Serial ports, also called COM ports, are used to connect devices, such as modems, through a serial interface meaning one data bit in succession of another. It's located on the back of a PC. Particularly, it was a 9-pin and 25-pin male format. Their transmission speed is limited to 57KBps and a maximum cable length of 50 feet.


USB ports were implemented on computers 1995 and became standard on most computers in 1998. They are a different type of serial port with the name comeing from it being able to connect a wide variety of different devices including keyboards, printers, mice and scanners. It's designed to be plug-and-play, an ability that both parallel and standard serial ports lack. It's also expandable with the use of USB hubs that give addition USB ports if needed, another capability lacking with its predecessors. USB has several different specifications which increases its performance. Its first incarnation had transmission speeds of 12 MBps (megabytes per second) and increased to up 480 MBps in version 2.0 making it considerably faster than the older form factors.

IEEE 1394 (FireWire)

Apple is the foremost pioneer of FireWire. FireWire ports run at data transfer speeds of 800 MBps. This speed can be maintained over a cable of 14 1/2 feet with FireWire 400 and over 300 feet for FireWire 800, longer than both parallel and standard serial.