Datasheet

42 Chapter 1
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Hardware
PCMCIA (Personal Computer Memory Card
International Association)
The PCMCIA standard defines the PC Card (formerly known as the PCMCIA Card), an
interface designed for laptop computers. This standard is discussed in more detail later in
this chapter.
Legacy Parallel and Serial
These buses are called legacy because they’re old technology and are being phased out. The
legacy serial port, also called an RS-232 port, is a 9-pin or 25-pin male connector. It sends
data one bit at a time and is usually limited to about 115Kbps in speed.
The legacy parallel port transfers data 8 bits at a time. It’s a 25-pin female connector.
A system typically has only one parallel port, but because many printers are now coming
with USB interfaces, this is no longer the inconvenience that it used to be.
PATA/IDE/EIDE Devices
IDE drives are the most common type of hard drive found in computers. But IDE is much
more than a hard drive interface; it’s also a popular interface for many other drive types,
including CD-ROM, DVD, and Zip. IDE drives are the most prevalent in the industry today.
IDE drives are easy to install and configure, and they provide acceptable performance for
most applications. Their ease of use relates to their most identifiable feature—the controller
is located on the drive itself.
IDE Technologies
The design of the IDE is simple: put the controller right on the drive, and use a relatively
short ribbon cable to connect the drive/controller to the IDE interface. This offers the
benefits of decreasing signal loss (thus increasing reliability) and making the drive easier
to install. The IDE interface can be an expansion board, or it can be built into the mother-
board, as is the case on almost all systems today.
IDE generically refers to any drive that has a built-in controller. The IDE we know
today is more properly called AT IDE; two previous types of IDE (MCA IDE and XT IDE)
are obsolete and incompatible with it.
There have been many revisions of the IDE standard over the years, and each one is
designated with a certain AT attachment (ATA) number—ATA-1 through ATA-8. Drives
that support ATA-2 and higher are generically referred to as enhanced IDE (EIDE).
With ATA-3, a technology called ATA Packet Interface (ATAPI) was introduced to help
deal with IDE devices other than hard disks. ATAPI enables the BIOS to recognize an IDE
CD-ROM drive, for example, or a tape backup or Zip drive.
Starting with ATA-4, a new technology was introduced called UltraDMA, supporting
transfer modes of up to 33Mbps.
ATA-5 supports UltraDMA/66, with transfer modes of up to 66Mbps. To achieve this
high rate, the drive must have a special 80-wire ribbon cable, and the motherboard or IDE
controller card must support ATA-5.
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