It's amazing how much has changed in computing over the last 10 to 15 years. We now have processors, graphics cards, and hard drives that can run rings around those of only a few years ago. As much as things have changed, however, there are still some aspects of computing that haven't changed much at all. Take the good old serial and parallel ports on the back of our PC's, for instance. They have changed very little over the course of time, and now represent a bottleneck to the continued advancement of the PC. Fortunately, there's a new type of port technology called the universal serial bus (USB) that promises to do away with the old serial and parallel ports once and for all.

Why do we want to get rid of serial and parallel ports? Well, there are a number of good reasons. First of all, these ports can only handle a limited bandwidth (115 Kbps for serial ports, approximately 2.5 Mbps for parallel ports). These speeds are too slow to handle the new ISDN modems, digital scanners, telephones, and other devices that push data at speeds far higher than these ports can handle. Secondly, these ports use up valuable interrupts (IRQ's) on your PC that could be used by other peripherals. For example, if you have two serial ports and a parallel port, you have already used up three of the 16 IRQ's available on your PC (numbers 3, 4, and 7, to be exact). Since several other devices in your PC are already assigned an IRQ of their own (your floppy drives are assigned IRQ 6, for example), it's easy to see how you need to free up as many IRQ's as possible. Furthermore, you can generally connect only a couple of devices in parallel up to each one of these ports before running into conflicts and performance issues.

The universal serial bus (USB) is the solution to all of the above mentioned problems. USB allows you to connect up to 127 devices to a single USB port, so you no longer have the problem of running out of physical ports or IRQ's. A USB keyboard, for instance, can have several USB ports on it, and can act as a hub for connecting other USB devices to the PC. Each cable connecting a USB device can be up to five meters long. USB also supports two bus speeds: a slower speed of 1.5 Mbps (for peripherals such as keyboards, modems, and scanners), and a higher speed of 12 Mbps (for things such as printers, monitors, and videophones). USB can support two or more devices running at either speed on the same line without conflicts. It also supports the "hot swapping" of peripherals, so you can plug a new device into the USB chain, and the operating system will automatically detect it and load the proper software drivers without user intervention. USB connectors have four pins on them, two of which supply power to the devices that are connected to them. This means that in the near future, you may be able to get rid of many of the power cords you currently have to plug into an outlet as well!

Microsoft is currently adding USB support to Windows 95 and Windows NT operating systems, and there are already a number of new PC's that are including USB ports as a standard component. Users owning PC's without USB ports will be able to add them to their systems through the use of expansion cards. Later in 1997, you'll begin to see peripherals such as modems and printers equipped with USB connectors (although most of them will also continue to supply serial and parallel ports for compatibility with the huge number of PC's out there without USB). This situation will continue for a few years until USB equipped PC's become commonplace, after which the old style serial and parallel ports will finally fade into history.

Gateway offers this column to its readership as a service, but please note that it is not responsible for the accuracy or opinions of the author and offers no warranty either expressed or implied that the information will produce the desired result.

The information provided in this article is based upon the writers particular experience with certain equipment. Familiarize yourself with the requirements of your local and state electrical code and insure yourself that the work you plan to do does not require a licensed professional. If you decide to attempt to do the work yourself, always exercise extreme caution when working on electrical systems because accidents may cause serious injury including death and damage your computer. If you experience difficulty or do not understand the instructions, please consult a professional in your area.

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