ATA
Short for AT Attachment, ATA was first approved May 12, 1994, under the ANSI document number X3.221-1994 and is an interface used to connect such devices as hard disk drives, CD-ROM drives, and other disk drives. The first ATA interface is now commonly referred to as PATA, which is short for Parallel AT Attachment after the introduction of SATA. Today, almost all home computers use the ATA interface, including Apple computers, which use SATA.
The ATA standard is backwards compatible, which means new ATA drives (excluding SATA) can be used with older ATA interfaces. Additionally, any new feature introduced is also found in all future releases. For example, ATA-4 has support for PIO modes 0, 1, 2, 3, and 4, even though these were first introduced in ATA-1 and ATA-2.
Below is a listing of each of the ATA, IDE, and EIDE standards to help provide a better understanding of the history behind this interface, as well as an understanding of each interface's capabilities.
ATA / ATA-1 / IDE
ATA was first developed by Control Data Corporation, Western Digital, and Compaq and first utilized an 8-bit or 16-bit interface with a transfer rate of up to 8.3MBps, and support for PIO modes 0, 1, and 2. Today, ATA and ATA-1 are considered obsolete.
ATA-2 / EIDE / Fast ATA / Fast IDE / Ultra ATA
ATA-2, more commonly known as EIDE, and sometimes known as Fast ATA or Fast IDE, is a standard approved by ANSI in 1996 under document number X3.279-1996. ATA-2 introduces new PIO modes of 3 and 4, transfer rates of up to 16.6MBps, DMA modes 1 and 2, LBA support, and supports drives up to 8.4GB. Today, ATA-2 is also considered obsolete.
ATA-3 / EIDE
ATA-3 is a standard approved by ANSI in 1997 under document number X3.298-1997. ATA-3 added additional security features and the new S.M.A.R.T feature.
ATA-4 / ATAPI-4 / ATA/ATAPI-4
ATA-4 is a standard approved by ANSI in 1998 under document NCITS 317-1998. ATA-4 includes the ATAPI packet command feature, introduces UDMA/33, also known as ultra-DMA/33 or ultra-ATA/33, which is capable of supporting data transfer rates of up to 33MBps.
ATA-5 / ATA/ATAPI-5
ATA-5 is a standard approved by ANSI in 2000 under document NCITS 340-2000. ATA-5 adds support for Ultra-DMA/66, which is capable of supporting data transfer rates of up to 66MBps, and has the capability of detecting between 40 or 80-wire cables.
ATA-6 / ATA/ATAPI-6
ATA-6 is a standard approved by ANSI in 2001 under document NCITS 347-2001. ATA-6 added support for Ultra-DMA/100 and has a transfer rate of up to 100MBps.
ATA layout
The above ATA interfaces on a 3.5-inch disk drives have a 40-pin connector and are capable of supporting up to two drives per interface. Note: 2.5-inch hard disk drives use a 50-pin connector and PCMCIA utilizes a 68-pin connector. Below is a description of each of the pins on a 40-pin ATA interface.
| Pin | Function | Pin | Function |
| 1 | Reset | 2 | Ground |
| 3 | Data 7 | 4 | Data 8 |
| 5 | Data 6 | 6 | Data 9 |
| 7 | Data 5 | 8 | Data 10 |
| 9 | Data 4 | 10 | Data 11 |
| 11 | Data 3 | 12 | Data 12 |
| 13 | Data 2 | 14 | Data 13 |
| 15 | Data 1 | 16 | Data 14 |
| 17 | Data 0 | 18 | Data 15 |
| 19 | Ground | 20 | Key |
| 21 | DDRQ | 22 | Ground |
| 23 | I/O Write | 24 | Ground |
| 25 | I/O Read | 26 | Ground |
| 27 | IOC HRDY | 28 | Cable Select |
| 29 | DDACK | 30 | Ground |
| 31 | IRQ | 32 | No Connect |
| 33 | Addr 1 | 34 | GPIO_DMA66_Detect |
| 35 | Addr 0 | 36 | Addr 2 |
| 37 | Chip Select 1P | 38 | Chip Select 3P |
| 39 | Activity | 40 | Ground |
- See the Integrated Drive Electronics (IDE) definition for a graphical representation of the cables, ports, and connections relating to ATA.
- ATA, ATAPI and other computer interfaces help and support.
Also see: ATAPI, EIDE, IDE, Hard disk drive definitions, SATA