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- This Week's Free Computer Tip -

146 - What is USB and why do I care?

The rapid advances in computer hardware over the years have been truly stunning. We are so used to this happening that we take for granted that our next computer will be bigger, faster and cheaper. Almost unnoticed in all these improvements was the announcement of "USB", the Universal Serial Bus. It was an entirely new way to connect hardware devices (disk drives, printers, digital cameras, etc.) to our computers. (Big yawn here. The truth is, we don't care how the computer works, as long as it works, right?) Well, for the consumer, this one improvement moved us out of the dark ages in terms of the computer hardware. This week's bulletin will tell you what you need to understand about USB and why it makes your life so much easier.

If you already know all about USB, just skip to the Shopping and Buying Tips, below.

Before USB (background) -
You may have forgotten already but before USB came along, deciding to add a new printer or a second hard disk was a technical nightmare. Computers all had what they called "interrupts" and each device was assigned to an interrupt. What these interrupts did was this. When the computer is working, the main processor is busy doing it's thing, the disk is spinning, the printer is printing, etc., and seemingly all at once. However, beneath all of those goings on, the computer never knows ahead of time when the printer is going to need its attention. In the grand scheme of things, there has to be some way to tell the main processor that something that needs attention has happened over at the printer, and that's where the interrupt comes in. The interrupt sends a signal to the processor chip that basically says, "Hey, stop what you're doing for a second and send me some more data to print." or, "Stop what you're doing and tell the owner I just ran out of paper". There are many more examples, but those two should at least give you the idea. Interrupts are signals to the main processor to tell it that it needs to pay some brief attention to a peripheral device.

Unfortunately, the original design for interrupts did not anticipate the vast array of peripheral devices which would eventually come along. The original design only allowed for a very limited number of interrupt circuits to be built into a computer chip (about a dozen or so) and the processor itself used most of them. There were only a handful left available for adding new hardware and consumers soon ran out of them.

Peripheral manufacturers tried to make it easy for us, but only added to the confusion. They would try to take the guesswork out of it for us by designing their hardware to use a particular interrupt (let's say, interrupt 5), making it their "default" interrupt for the tape drive backup device they were trying to sell to us. That was fine except that the manufacturer of the scanner we already owned, had also chosen interrupt 5 for his device! Now what? The poor consumer shouldn't have to know from interrupts! Then came the final blow. We would read the instructions which came with our new tape drive and they would tell us to change the interrupt for the other guy's device, as if we would know how to do that! You had to have a PHD in computer hardware, simply to add a new tape drive! In two short paragraphs, I can't really do justice to how difficult it was back then. For the consumer, it was a big mess.

Along comes USB -
Some engineer out there somewhere deserves a gold star. USB eliminated all of the previous problems. With USB, we never have to deal with interrupts ever again. They're still in there, but we don't need to ever know about them. To install a new hardware device, we simply plug it in. There is no more worrying about whether our computer is using interrupt 5 or not. We don't care. Up to 255 devices can now be plugged into a single USB connection and we could care less how the computer keeps track of all of that. The computer industry envisioned "Plug-and-Play" for years, but this made it happen.

In no time at all, every new computer came with at least one USB connection, usually on the back of the computer. These days, it's hard to find a PC which doesn't come with it. USB connections are the ones that are flat and rectangular and about half an inch wide. Unlike other types of computer cables, they have no pins. You will usually find at least two USB ports on the back of a computer plus one or two on the front. (Digital cameras often plug into these USB ports to download their photos, so the plugs have been placed on the front of the computer for convenience.) USB comes in two speeds now (known as USB 1.1 and USB 2.0). Both are fast but 2.0 is even faster. Here again, they did it right. Any USB device will run in any USB connection because USB 2.0 is backward compatible. Plug a USB 1.1 device into a USB 2.0 port, and it runs just fine (just at the slower speed).

The bottom line to this is, you don't need to know anything technical to plug in your next peripheral. Is that kool, or what!

Shopping and Buying Tips -
I mentioned that there are two speeds of USB available now. Version 2.0 is forty times (40x) faster than version 1.1. That's a big deal difference when you are moving a lot of data, as in copying files during a backup. There is no difference in the physical connectors or the cables themselves and, in spite of what the retailers would have you believe, "premium" cables with gold tips and all, are no faster or more reliable than standard cables.

Tip #1 (1.1 verses 2.0) -
Choose version 2.0 whenever you have that buying choice. In the case of an external hard disk, the times for a typical full-system backup will be under an hour verses four hours. Any device which passes a lot of data will run noticeably faster when connected with USB 2.0. (In relative terms, printers, keyboards, and mice are slow devices where scanners and disk drives are fast.)

Tip #2 (Upgrading to 2.0) -
If your computer has USB ports, but they are version 1.1 (this would normally be computers that were manufactured 4 or 5 years ago), you can add a card to the computer which will give you several USB 2.0 ports. The card I added to mine cost about $30 and gave me 4 of the 2.0 ports. I would consider this if I wanted to run external disk drives or scanners (see tip #1).

Tip #3 (using USB Hubs when you run out of ports) -
If you have used all your USB ports, how do you add more peripherals? This is easy too. You buy an inexpensive device known as a "USB hub". They will be called 4-port or 8-port USB Hubs, denoting how many physical connections they come with. Because your computer doesn't care how USB devices are connected (USB is great), all you do is this. Unplug any one of the USB devices you already have plugged into your computer and plug in the hub in its place. Then, plug in the former device into any one of the hub ports. Now, add your new device to any one of the remaining open hub ports. That's it. You're done. Up to 255 peripherals can be added to your system in this fashion.

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