NWA-PCUG Newsletter Article, August 2010
USB Explained
By Sandy Berger, CompuKISS
sberger (at) compukiss.com (click to email author) -->

USB, or Universal Serial Bus, is a hardware bus standard that allows users to plug a peripheral device into a USB port and have it automatically configured and ready to use. It is one of the success stories of the personal computer. It not only works well, but also makes the life of the average computer user easier.

Most computers that were manufactured after 1995 have USB ports. Windows 95 had only erratic support for USB, but all newer Windows operating systems have support for USB. iMacs and other Apple computers also support USB.

So what's the big deal about USB? USB has a lot going for it. It has three great features: speed, power, and ease of use.

What's a Port?
A port is an interface for attaching external devices to a computer. The original IBM personal computers came with two ports -- a serial port and a parallel port. Typically, devices such as modems were attached to the serial port and devices such as printers connected to the parallel port. Another type of port called the SCSI port became a mainstay in the Mac world but never caught on in a big way in the PC world.

Ports not only connect an external device, but also control the transfer rate, the rate at which data can be transferred between the computer and the attached device. This is where the USB port excels. On the average, USB allows data to travel ten times the speed of the normal parallel port. It is also faster than a serial port. This means that a USB printer or scanner can operate faster than a printer or scanner that hooks up to the parallel port. The average serial port transfer rate is 150 kbps; the parallel port is 1.2 mbps. The USB port transfers data up to 12 mbps depending on the type of device that is connected.

Because USB ports are so much faster and easier to use, they have almost completely eliminated parallel and serial ports.

What Does USB Look Like?
To find the USB port on your computer, look at the back or front of your desktop computer or on the side of your laptop computer. Older ports had rows of small pins or pinholes where peripherals can be plugged in. The USB port looks slightly different. It is a small thin opening about Ĺ " long. It has no obvious pins or pinholes. It is often, but not always, marked "USB.Ē Most of today's computers have two or more USB ports. Many desktops even have the added convenience of USB ports in the front of the computer as well as the back, a boon for devices like cameras, which are hooked up and removed often.

Why not take something good and make it even better? Thatís just what the computer industry did with USB 2. With a maximum transfer rate of 480 mbps, or 60 mb per second, USB 2 is 40 times faster than USB 1. Better yet, it is backwardly compatible with USB 1. That means that if your new computer comes with USB 2, you can still use your old USB devices. Of course, they will perform at USB 1 speeds, but they will still work properly. To take full advantage of the speed of USB 2, the devices that you purchase must be USB 2 enabled and must be run from a USB 2 port. These speedy devices have already made their appearance and are sure to be plentiful in the future. The speed of USB 2 will be beneficial to many devices including digital cameras, hard drives, and DVD drives. To recognize a USB 2 port or device, look for the USB High-Speed logo.

Since the computer world never seems to stand still, USB 3 is now in the works. Of course, USB 3 will be even faster than USB 1 or 2.

Stackable & Swappable
USB has other advantages as well. Although I can't imagine why anyone would want to, you can attach up to 127 devices to one USB port. USB ports are self-powered, so you can say goodbye to those big chunky power blocks.

If you run out of USB ports, you can add a USB hub. This is a small device that will plug into one USB port and give you ports for two, four, or even more USB devices. However, if you attach more than a few devices, you will need to add a self-powered hub, which is a small mechanism that provides extra power to the attached devices.

The idea behind USB is that the devices will be daisy-chained together. The USB device that you purchase may have another built-in USB port so you can hook other devices to it. Many of the USB monitors that I've seen come with three USB ports for attaching other devices. Some USB keyboards also have several built-in USB ports where you can hook up other devices. For instance, your mouse might connect to your keyboard, your keyboard to your monitor, and your monitor to your computer. This eliminates the mess of power cables that often accompany a computer system.

USB devices are hot swappable. You can plug in and remove any USB devices without turning the computer on and off. This is a great feature for those of us who want to purchase only one peripheral to use on two or more computers. Itís also great for devices like cameras that are attached and removed from the computer often.

USB Devices
You can plug just about anything into a USB port: keyboards, cameras, mice, joy sticks, modems, zip drives, floppy drives, printers, and scanners. You can even purchase USB speakers to produce great digital sound on your computer.

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