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Parallel ATA

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Parallel ATA, often called PATA, is a standard interface for computer storage. It allows a computer to communicate with devices like hard disks, floppy disks, and optical drives.

ATA Plug
ATA Plug

This technology was essential for many years because it provided an inexpensive way to connect storage to a system. While it has largely been replaced by Serial ATA (SATA) in modern computers, PATA remains a significant part of computing history. The standard is currently maintained by the X3/INCITS committee.

PATA-cable
PATA-cable

The mechanism of PATA relies on a major shift in how hardware is controlled. In older systems, a separate controller card was needed to manage the mechanical parts of a drive. PATA uses Integrated Drive Electronics, or IDE, which means the controller is built directly into the drive itself.

IDE Connectors in PCChips M925LR Pentium 4
IDE Connectors in PCChips M925LR Pentium 4

Instead of the computer managing the movement of the disk head arm, the host computer simply asks for a specific 512-byte block of data. The drive's internal controller then handles the mechanical tasks of finding and reading that sector. This integration relieved the computer's motherboard of many complex chores.

As the technology evolved, different standards and versions emerged. The original interface was known as ATA or AT Attachment, designed for the 16-bit ISA bus. In 1994, the ATA-1 standard was officially recognized. Later, the ATA-2 specification introduced several enhancements. One major addition was the ATAPI, or ATA Packet Interface.

{{Not a typo
{{Not a typo

80-pin parallel ATA interface on a 1.8" hard disk] ATAPI allowed the interface to support devices other than hard drives. It works by embedding SCSI commands into packets for transmission over the ATA cable. This allowed for the use of removable media, such as CD and DVD drives, which require specific commands like "media eject."

The history of PATA began with a collaboration between Western Digital and Compaq in 1986. They developed the IDE interface to remain compatible with existing IBM PC hard drive software. The first such drives appeared in Compaq computers in 1986, followed by a separate offering from Conner Peripherals in June 1987. For a long time, these interfaces were found on host bus adapters or sound cards. Eventually, they became embedded directly into the Southbridge chip on a computer's motherboard. In 2003, the introduction of SATA led to the original ATA being officially renamed Parallel ATA to avoid confusion.

Performance and capacity have changed significantly through different versions. The ATA/ATAPI-4 standard introduced Ultra DMA transfer modes. These modes initially supported speeds between 16 and 33 MB/s. Later versions of PATA can reach speeds of up to 133 MB/s. To achieve these higher speeds, newer versions required 80-wire cables to reduce electrical interference known as crosstalk.

ATA cables
ATA cables

Capacity also grew through different addressing modes. The first interfaces used 22-bit addressing, limiting capacity to 2 gigabytes. The LBA28 mode used 28-bit addressing, which allowed for a maximum of 128 GiB or 137 GB. Later, ATA-6 introduced 48-bit addressing to allow for even larger drives.

One surprising aspect of PATA history involves the limitations of the system BIOS. Early BIOS software often had artificial limits on how large a drive could be. One limit occurred at 504 MiB because some BIOSes could not handle certain numerical values. Another famous limit was the 8.4 gigabyte barrier, caused by limits in both the BIOS and MS-DOS.

To fix this, manufacturers sometimes included small programs to override these limits during startup. Eventually, the Enhanced Disk Drive (EDD) extension allowed for much larger addressing.

Parallel ATA technology still connects to several modern or specialized systems. For example, Compact Flash memory cards use a miniature version of the IDE-ATA interface to function.

Compact Flash is just a miniature IDE-ATA interface
Compact Flash is just a miniature IDE-ATA interface

You can also find PATA to USB adapters, which allow older drives to connect to modern machines.

LG Super Multi GSA-E40N - PATA 2 USB Adapter-8672
LG Super Multi GSA-E40N - PATA 2 USB Adapter-8672

Understanding PATA helps explain how computer storage moved from complex, external controllers to the integrated, high-speed systems we use today.

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🖼️ Images & Media (8)
File:PATA-cable.jpg
PATA-cable.jpg
File:IDE Connectors in PCChips M925LR Pentium 4.jpg
IDE Connectors in PCChips M925LR Pentium 4.jpg
File:ATA Plug.svg
ATA Plug.svg
File:1992 80386 PC AMD 386DX-40 no onboard IDE floppy serial parallel sound video or network.jpg
1992 80386 PC AMD 386DX-40 no onboard IDE...
{{Not a typo
File:ATA cables.jpg
ATA cables.jpg
File:LG Super Multi GSA-E40N - PATA 2 USB Adapter-8672.jpg
LG Super Multi GSA-E40N - PATA 2 USB...
File:Compact Flash is just a miniature IDE-ATA interface.jpg
Compact Flash is just a miniature IDE-ATA...
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