Chapter 10. Interfaces

If you could pry one of the expansion bus connectors off the motherboard of your computer and solder a length of cable to it, you'd probably ruin your computer. But you'd also make the equivalent of a mass storage interface. This may be educational, but don't try it at home. Not only will it be expensive and wasteful (of your computer), but unnecessary. Some clever engineers have already done it for you.

In fact, the most popular interface for hard disk, CD, and DVD drives, is nothing more than a pried-off expansion board connector. The AT Attachment interface earned its name by putting the AT expansion bus connector on a short cable that plugged into hard disk drives. The interface has matured somewhat since then—it's about 16 times faster, has developed its own language, and trimmed off a lot of fat. But deep down, underneath all the gloss and the layers of specifications, is the heart of the AT expansion bus.

At that, AT Attachment is almost the perfect interface. It brings devices both electrically and logically closer to your computer's circuitry than any other connection system. And that's exactly what the interface is supposed to do—connect individual devices to your computer.

AT Attachment isn't the only popular interface, however. It has a number of rivals and predecessors. If you have a high-performance computer and disk system, you're likely to covet its closet rival, SCSI, for its speed and versatility—or even ATA's designated successor, Serial ATA, which promises to be the fastest yet lowest cost interface developed so far.

At the other end of the spectrum, your computer likely also has the slowest interface in common use still stuffed within its circuitry—a floppy disk interface. You probably don't need an engineering degree to figure out what it does. It runs the floppy disk drive that is the one remaining (or at least the most prominent) vestige of the technology of the first personal computer in modern machines. It's the equivalent of you wearing your grandmother's locket around your neck.