Hardware Reference
In-Depth Information
Interface for Disk Drives.” ATA-1 was officially withdrawn as a standard on August 6,
1999.
Although ATA-1 supported theoretical drive capacities up to 136.9GB (2
28
−2
20
=
267,386,880 sectors), it did not address BIOS limitations that stopped at 528MB (1024
× 16 × 63 = 1,032,192 sectors). The BIOS limitations would be addressed in subsequent
ATA versions because, at the time, no drives larger than 528MB existed.
ATA-2 (ATA Interface with Extensions-2)
ATA-2wasamajorupgradetotheoriginalATAstandard.Perhapsthebiggestchangewas
almost a philosophical one. ATA-2 was updated to define an interface between host sys-
tems and storage devices in general and not only disk drives. The major features added to
ATA-2 compared to the original ATA standard include the following:
• Faster PIO and DMA transfer modes
• Support for power management
• Support for removable devices
• PCMCIA (PC Card) device support
• Identify Drive command that reports more information
• Defined standard CHS/LBA translation methods for drives up to 8.4GB in capacity
The most important additions in ATA-2 were the support for faster PIO and DMA modes,
aswellasmethodstoenableBIOSsupportupto8.4GB.TheBIOSsupportwasnecessary
because although ATA-1 was designed to support drives of up to 136.9GB in capacity, the
PC BIOS could originally handle drives of up to 528MB. Adding parameter-translation
capability now allowed the BIOS to handle drives up to 8.4GB. This is discussed in more
detail later in this chapter.
ATA-2 also featured improvements in the Identify Drive command that enabled a drive to
tellthesoftwareexactlywhatitscharacteristicsare;thisisessentialforbothPlugandPlay
(PnP) and compatibility with future revisions of the standard.
ATA-2 was also known by unofficial marketing terms such as Fast-ATA or Fast-ATA-2
(Seagate/Quantum) and EIDE (Enhanced IDE, Western Digital).
Although work on ATA-2 began in 1993, the standard was not officially published until
1996as“ANSIX3.279-1996ATAttachment Interface withExtensions.” ATA-2wasoffi-
cially withdrawn in 2001.
