The ATA/IDE Interface - Upgrading and Repairing PCs - page 451

Chapter 7. The ATA/IDE Interface
An Overview of the IDE Interface
The interface that connects disk drives to a PC is typically called IDE (Integrated Drive
Electronics);however,theofficialnameofthisinterfaceisATA(ATAttachment).TheATA
designation refers to the fact that this interface was originally designed to connect a com-
bined 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 inter-
face,IDEisamarketingtermoriginatedbysomeofthedrivemanufacturerstodescribethe
drive/controller combination used in drives with the ATA interface. Integrated Drive Elec-
tronicsreferstothefactthattheinterfaceelectronics orcontrollerisbuiltintothedriveand
is not a separate board, as with earlier drive interfaces. Although the correct name for the
particular IDE interface we most commonly use is technically ATA, many persist in using
theIDEdesignationtoday.Ifyouarebeingpicky,youcouldsaythatIDErefersgenerically
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 simul-
taneously down the interface cable. A newer interface called Serial ATA (SATA) was of-
ficially 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 inter-
face 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 spe-
cifically 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