The ATA/IDE Interface - Upgrading and Repairing PCs - page 366

Chapter 7. The ATA/IDE Interface
An Overview of the IDE Interface
The interface used to connect disk drives to a PC is typically called IDE (Integrated Drive
Electronics); however, the official name of this interface is ATA (AT Attachment). The ATA
designation refers to the fact that this interface was originally designed to connect a combined drive
and controller directly to the 16-bit bus found in the 1984 vintage IBM PC-AT (Advanced
Technology) and compatible computers. The AT bus is otherwise known as the ISA (Industry
Standard Architecture) bus. Although ATA is the official name of the interface, IDE is a marketing
term originated by some of the drive manufacturers to describe the drive/controller combination used
in drives with the ATA interface. Integrated Drive Electronics refers to the fact that the interface
electronics or controller is built into the drive and is not a separate board, as it was with earlier
drive interfaces. Although the correct name for the particular IDE interface we most commonly use is
technically ATA, many persist in using the IDE designation today. If you are being picky, you could
say that IDE refers generically to any drive interface in which the controller is built into the drive,
whereas ATA refers to the specific implementation of IDE that is used in most PCs.
ATA was originally a 16-bit parallel interface, meaning that 16 bits are transmitted simultaneously
down the interface cable. A newer interface called Serial ATA (SATA) was officially introduced in
late 2000 and was adopted in desktop systems starting in 2003 and in laptops starting in late 2005.
SATA sends one bit down the cable at a time, enabling thinner and smaller cables to be used, as well
as providing higher performance due to the higher cycling speeds it enables. Although SATA is a
completely different physical interface design, it is backward compatible on the software level with
Parallel ATA (PATA). Throughout this topic, ATA refers to both the parallel and serial versions.
PATA refers specifically to the parallel version, and SATA refers specifically to the serial version.
Precursors to IDE
Several types of hard disk interfaces have been used for PC hard disks over the years, as shown in
Table 7.1 . As time has passed, the number of choices has increased; however, many of the older
interface standards are obsolete and no longer viable in newer systems.
Table 7.1. PC Drive Interfaces