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[ The PC Guide | The PC Buyer's Guide | Designing and Specifying PC Systems and Components | Designing PCs: Structure and Subsystems | PC Subsystem Design ]

Communications Subsystem

The communications subsystem of the PC is responsible for allowing the PC to communicate and interface with the "outside world". These components let the PC connect to other computers in a local network, to the Internet for world-wide data sharing, or to external add-on peripherals. Here are the components usually found in this group:

  • Modems, including analog modems, cable modems and others.
  • Network cards.
  • Serial and parallel communications ports.
  • USB (universal serial bus) ports. Since some storage devices commonly connect through USB I consider its controller part of the storage subsystem as well.
  • PC Card slots (for notebooks).

Regular serial and parallel communications ports have been standard since the very first PC; they have changed slowly over time but still perform the same general functions. It is still standard for at least one serial port and one parallel port to be found on most PCs. The controllers for these hardware ports are integrated on the motherboard on almost all modern machines, so they do not come up much in purchasing decisions: they are sort of "along for the ride". The only difference between systems is generally how many ports they have.

USB is a relatively new interface that has grown rapidly in popularity over the last few years. It supports a variety of devices ranging from storage to input to networking. It is a must for new systems, but beyond looking for support for it, there's not much to be concerned with.

A modem or equivalent hardware to allow Internet access is a virtual necessity today (sorry about that pun, I couldn't resist! :^) ) Most new PCs come with regular analog modems; if you are using a more advanced digital method of accessing the 'net you will need to purchase additional hardware. From the standpoint of the PC's hardware, modems are usually "add-in" cards and fairly standard in terms of their interface. You must match them to the system bus of the motherboard but otherwise they do not affect other hardware purchases significantly.

Like USB, network cards have gone from obscurity to popularity in a few years. At first only businesses made use of networks, but now many multiple-PC homes are setting up simple networks for file and peripheral sharing, gaming, and backup purposes. As with modems, network cards are pretty much independent of other hardware in the system and can be added after a system is purchased.

Next: Multimedia Subsystem

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