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Last time around, we covered hard drives and video graphics. In this installment, we'll cover floppy disk drives, multi-I/O cards, and memory requirements for multimedia PC's.
Virtually any stand-alone PC, and most PC's connected to networks of any kind, require some means of loading software and/or data into them. While the keyboard remains an important means of entering data into the computer, it is still slow and cumbersome compared to other data input devices. Then, too, keyboards are designed only to transmit data into the computer; they are not designed, or intended, as an output device.
The primary means of loading large amounts of information, such as a software package, into a personal computer is the floppy disk drive. Unlike the hard drives we discussed last month, floppy disks are designed to be easily removed from one computer and transported to another.
The first floppy drives were designed to use disks that were 8 inches across. The IBM PC, however, from its inception, used floppy disks that were only 5-1/4 inches across. At first, these drives recorded on only one side of the disk, and held only 160 kilobytes (abbreviated KB) of information. As the PC became faster and more powerful, this was upgraded repeatedly. By the time the IBM AT debuted in 1984, the standard 5-1/4" floppy drive recorded on both sides of the diskette, which held up to 360 KB of data. With the introduction of the AT, however, a new, high-density 5-1/4" floppy and floppy drive came on the market, holding up to 1.2 megabytes (abbreviated MB) of information.
Despite the portability of these diskettes, however, there were, and still are, potential problems. For one thing, 5-1/4 inch floppies are easily damaged. Even a fingerprint in the wrong place can render them unusable. In addition, these diskettes take up a significant amount of space. Also, it is all too easy to erase them accidentally, despite the presence of a special notch in the outer jacket that must be open or uncovered for the diskette to be written to or erased. For these reasons, computer manufacturers began working on a new, more compact floppy disk and drive. In 1986, IBM's Convertible laptop computer was the first to use a floppy drive designed to handle diskettes that were only 3-1/2 inches across. These diskettes held 720 KB of data. In addition, the new 3-1/2 inch floppies were housed in a hard plastic outer shell, with a built-in "write-protect" tab. Besides taking up far less space than 5-1/4 inch floppies, these new diskettes were much less susceptible to damage than their predecessors. For these reasons, the new format grew rapidly in popularity in the PC community.
Less than a year later, with the introduction of its PS/2 line, IBM again set the trend by using a higher-density 3-1/2 inch floppy disk and drive. These new diskettes held 1.44 MB of data--twice as much as before. Once again, the new format rapidly became popular.
At the time I write this, 3-1/2 inch, 1.44 MB floppy drives are the accepted standard for PC use, with 5-1/4 inch, 1.2 MB floppies in second place. Most software packages now on the market for PC's are available only in the 1.44 MB format. For this reason, a 3-1/2 inch, 1.44 MB floppy will be our floppy drive of choice in the example system we are assembling. Both the 3-1/2 inch and the 5-1/4 inch floppy drives are fairly inexpensive, however (most times, you can get either type for well under $50), so we can easily add on a 5-1/4 inch drive if we need to.
As with hard disk drives, floppy disk drives require a controller card to enable them to exchange information with the remainder of the computer system. Usually, such a controller is combined with several other types of control circuitry, in what is commonly referred to as a "multi-I/O card."
In addition to video, several other types of output devices are available for use in PC's. Printers generally use what is called a "parallel port" (so called because the data travels along the electronic equivalent of a multi-lane highway or freeway), while such devices as modems, some makes and models of PC mice, etc., use what is commonly referred to as a "serial port" (a name derived from the fact that the data travels along the wires in "single-file" fashion, like on a one-lane country road). As a general rule, most PC's have at least one parallel and two serial ports.
In order to save both space and money, these multiple circuits, and often an IDE hard disk interface circuit as well, are customarily manufactured together in a "multiple input/output," or "multi-I/O," card. These cards, which are generally among the most inexpensive of all PC expansion cards (most are less than $50), are available in ISA, VESA Local Bus, and PCI Local Bus models. In our example system, since we already have a VESA Local Bus IDE controller card for our hard disk drive, we'll use an ISA multi-I/O card.
We come now to one of the most problematic areas of PC usage: main memory requirements. All personal computers use what is called "random access memory," or RAM, for short-term storage and computation. As software packages become larger and more powerful, the amount of memory they require also increases -- often quite dramatically.
At this writing, multimedia PC systems require a minimum of 8 megabytes of RAM, and 16 MB or more is recommended. While it might seem foolish to buy more RAM than you currently think you need, the extra storage space can often be put to good use. By holding some parts of the computer's main operating system, as well as other programs, in RAM, the operation of the computer as a whole can be considerably speeded up. This task is accomplished by means of special utility programs called "memory managers." QEMM from Quarterdeck Systems is one popular program of this type.
For a variety of reasons, prices for RAM tend to vary quite widely. In our example multimedia PC, we'll start off with 16 MB of RAM. We can easily add on more memory later on if we need to. At the time I write this, the price for RAM is hovering around $35 per megabyte, depending on the specific type of memory module being used. To find out what kind of RAM module your system requires, check the manual provided with your motherboard.
In our next installment, we'll cover three of the most essential parts of a multimedia PC: modems, mice, and sound cards.
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