Evolution of I/O Connections in Computing
By David Pheteplace, Bishop & Associates Inc.

The last 50 years have brought about significant changes to interconnect topologies, and input/output (I/O) connections on computers are no exception. The evolution has taken us from very specialized application-specific I/O connections to highly standardized, miniaturized connectors and interconnects.
At the inception of the personal computer revolution in the 1970s, D-subminiature and ribbon connectors were utilized for most connections—from printer ports and floppy drives to the CRT screens and keyboards. The connections were not standard between various computer manufacturers and most of the peripherals were external, so there was a proliferation of cabling. The early networking needs were often met with different types of RF connectors, such as those used in the IBM token ring architecture.

During the 1980s, two changes occurred. First, VLSI (Very Large Scale Integration) put more circuits onto individual computer chips and brought the peripherals inside the computer case—hence less I/O connections were needed. Secondly, the move to miniaturize connectors and standardize the interconnect architecture began, creating compatibility between different computer and peripheral manufacturers. The miniDIN connectors gained favor for keyboard and mouse applications. The Small Computer System Interface (SCSI) connector, and its standardized operating system architecture, began to make inroads in the late 1980s, but variations of its application were still in use. We also saw the use of RJ11 connectors as the standard modem interconnect.

The 1990s saw the development of SCSI 2, which enabled better compatibility between manufacturers, and the beginnings of IEEE 1394 (FireWire), USB (Universal Serial Bus) and Ethernet-over-twisted-pair-wires terminated with RJ45 telecom connectors. Each of these interconnect schemes have gone through their own evolution, but all contributed to a significant degree of standardization for the I/O function. In the current decade, 1394 is now the standard for high-speed, video connection between video recording devices and PCs. USB (now USB 2) is the de facto plug-and-play interconnect for a variety of devices, including printers, external hard drives, scanners, memory sticks/thumb drives, broadband cards, and webcams--with almost universal compatibility between manufacturers.

Another connector series that started in the late 1990s was PCMCIA 16 bit bus, which uses the PC card connector. These were intended for use with Ethernet cards, broadband cards, and external drives. Smaller versions of this 68-pin connector are commonly used in a variety of memory cards for digital cameras. Multimedia PCs often have a variety of these connectors to accept different memory card configurations.

I/O Connectors Today
Today’s typical PCs have a variety of connectors. The most common are:

  • Two or more USB connector ports to hook up printers, external drives, etc.

  • An RJ45 port for Ethernet

  • An RJ11 connector for phone modems

  • A 9-pin D-sub for analog monitors and/or a DVI connector for digital monitors

  • A 1394 connector for video connections

  • Two audio connectors for a microphone and speakers/headphones

  • Laptop computers will typically have a PC card slot/connector.

  • Multimedia computers typically have RCA connectors for analog video/sound processing. They also typically have a variety of smaller memory card connectors for downloading data from digital cameras.

And, not all of the connections use connectors. Wireless Local Area Network (WLAN) built into your computer can get you onto the local network in the office or airport, without any cabling. Bluetooth can wirelessly connect your keyboard, mouse, and printer.

I/O Connectors Tomorrow
Certainly, we will see the introduction of devices with USB 3.0 in 2009/2010. According to USB.org, USB 3.0 will be backwards compatible and will have a 10X performance increase over USB 2.0. It will use less power and have improved protocol efficiency. The need for speed is being driven by digital media, which is driving file sizes over 25 gigabytes. USB 2.0 transmits about 480 Mbit/second, whereas 3.0 will run at 4.8 Gbit/second.

We’ll also likely see fiber optic connectors being employed as file sizes continue to grow, although there are no clear standards at this time.

 HDMI (High Definition Multimedia Interface), currently used with digital video recorders and HDTVs, could replace the DVI connectors/cables for digital monitors, and would offer a more compact interconnect scheme.

Wireless connections will also continue to grow. USB.org is also promoting WUSB (wireless USB), which could further eliminate some of the copper USB interconnect.

All photos are courtesy of Tyco Electronics.

David Pheteplace

Bishop & Associates Inc., Market Segment Director - Cable Assemblies
David Pheteplace joined Bishop & Associates in 2008 as its market segment director for cable assemblies. Pheteplace, a management consultant for the electronic and interconnect industry, specializes in operational and strategic analysis, problem solving, and solution implementation. He has more than 20 years of experience in the connector industry, including managing divisions for Amphenol, Cinch, and Robinson Nugent. Pheteplace can be reached at www.pheteplace.com.

 
 
 
 

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