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65-543: The standard is maintained by the X3/ INCITS committee. It uses the underlying AT Attachment (ATA) and AT Attachment Packet Interface ( ATAPI ) standards. The Parallel ATA standard is the result of a long history of incremental technical development, which began with the original AT Attachment interface, developed for use in early PC AT equipment. The ATA interface itself evolved in several stages from Western Digital 's original Integrated Drive Electronics (IDE) interface. As

130-772: A host adapter interfacing with the rest of the computer system. The remaining connector(s) plug into storage devices, most commonly hard disk drives or optical drives. Each connector has 39 physical pins arranged into two rows (2.54 mm, 1 ⁄ 10 -inch pitch), with a gap or key at pin 20. Earlier connectors may not have that gap, with all 40 pins available. Thus, later cables with the gap filled in are incompatible with earlier connectors, although earlier cables are compatible with later connectors. Round parallel ATA cables (as opposed to ribbon cables) were eventually made available for ' case modders ' for cosmetic reasons, as well as claims of improved computer cooling and were easier to handle; however, only ribbon cables are supported by

195-426: A cable can perform a read or write operation at one time; therefore, a fast device on the same cable as a slow device under heavy use will find it has to wait for the slow device to complete its task first. However, most modern devices will report write operations as complete once the data is stored in their onboard cache memory, before the data is written to the (slow) magnetic storage. This allows commands to be sent to

260-530: A cable, it should be configured as Device 0 . However, some certain era drives have a special setting called Single for this configuration (Western Digital, in particular). Also, depending on the hardware and software available, a Single drive on a cable will often work reliably even though configured as the Device 1 drive (most often seen where an optical drive is the only device on the secondary ATA interface). The words primary and secondary typically refers to

325-681: A desktop case similar to that of the IBM PC. It weighs 32 pounds (15 kg) and is approximately 19.5 inches (50 cm) wide by 16 inches (41 cm) deep by 5.5 inches (14 cm) high. Similarly to the original IBM PC, the XT main board included a socket for the Intel 8087 floating point arithmetic coprocessor . This optional chip, when installed, greatly accelerated arithmetic for such applications as computer aided design or other software that required large amounts of arithmetical calculations. Only software that

390-448: A drive to a host with an ATA-5 or earlier interface will limit the usable capacity to the maximum of the interface. Some operating systems, including Windows XP pre-SP1, and Windows 2000 pre-SP3, disable LBA48 by default, requiring the user to take extra steps to use the entire capacity of an ATA drive larger than about 137 gigabytes. Older operating systems, such as Windows 98 , do not support 48-bit LBA at all. However, members of

455-496: A maximum drive capacity of two gigabytes. Later, the first formalized ATA specification used a 28-bit addressing mode through LBA28 , allowing for the addressing of 2 ( 268 435 456 ) sectors (blocks) of 512 bytes each, resulting in a maximum capacity of 128  GiB (137  GB ). ATA-6 introduced 48-bit addressing, increasing the limit to 128 PiB (144 PB ). As a consequence, any ATA drive of capacity larger than about 137 GB must be an ATA-6 or later drive. Connecting such

520-666: A problem in MS-DOS limited the number of heads to 255. This totals to 8 422 686 720 bytes (8032.5 MiB ), commonly referred to as the 8.4 gigabyte barrier. This is again a limit imposed by x86 BIOSes, and not a limit imposed by the ATA interface. It was eventually determined that these size limitations could be overridden with a small program loaded at startup from a hard drive's boot sector. Some hard drive manufacturers, such as Western Digital, started including these override utilities with large hard drives to help overcome these problems. However, if

585-481: A result, many near-synonyms for ATA/ATAPI and its previous incarnations are still in common informal use, in particular Extended IDE (EIDE) and Ultra ATA (UATA). After the introduction of SATA in 2003, the original ATA was renamed to Parallel ATA, or PATA for short. Parallel ATA cables have a maximum allowable length of 18 in (457 mm). Because of this limit, the technology normally appears as an internal computer storage interface. For many years, ATA provided

650-619: A sound card but ultimately as two physical interfaces embedded in a Southbridge chip on a motherboard. Called the "primary" and "secondary" ATA interfaces, they were assigned to base addresses 0x1F0 and 0x170 on ISA bus systems. They were replaced by SATA interfaces. The first version of what is now called the ATA/ATAPI interface was developed by Western Digital under the name Integrated Drive Electronics (IDE). Together with Compaq (the initial customer), they worked with various disk drive manufacturers to develop and ship early products with

715-406: A way for the host to determine whether the media is present, and these were not provided in the ATA protocol. ATAPI is a protocol allowing the ATA interface to carry SCSI commands and responses; therefore, all ATAPI devices are actually "speaking SCSI" other than at the electrical interface. The SCSI commands and responses are embedded in "packets" (hence "ATA Packet Interface") for transmission on

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780-503: Is a designation that has been primarily used by Western Digital for different speed enhancements to the ATA/ATAPI standards. For example, in 2000 Western Digital published a document describing "Ultra ATA/100", which brought performance improvements for the then-current ATA/ATAPI-5 standard by improving maximum speed of the Parallel ATA interface from 66 to 100 MB/s. Most of Western Digital's changes, along with others, were included in

845-739: Is an ANSI -accredited standards development organization composed of Information technology developers. It was formerly known as the X3 and NCITS . INCITS is the central U.S. forum dedicated to creating technology standards. INCITS is accredited by the American National Standards Institute (ANSI) and is affiliated with the Information Technology Industry Council, a global policy advocacy organization that represents U.S. and global innovation companies. INCITS coordinates technical standards activity between ANSI in

910-493: Is an expansion chassis using an identical case and power supply to the XT, but instead of a system board, provides a backplane with eight card slots. It connects to the main system unit using an Extender Card in the system unit and a Receiver Card in the Expansion Unit, connected by a custom cable. The 5161 shipped with a 10 MB hard drive, and had room for a second one. The Expansion Unit can also contain extra memory, but

975-597: Is defined in the MMC SCSI command set. ATAPI was adopted as part of ATA in INCITS 317-1998, AT Attachment with Packet Interface Extension (ATA/ATAPI-4) . The ATA/ATAPI-4 standard also introduced several " Ultra DMA " transfer modes. These initially supported speeds from 16 to 33 MB/s. In later versions, faster Ultra DMA modes were added, requiring new 80-wire cables to reduce crosstalk. The latest versions of Parallel ATA support up to 133 MB/s. Ultra ATA, abbreviated UATA,

1040-558: Is guided by its Executive Board . The INCITS Executive Board established more than 40 Technical Committees, Task Groups and Expert Groups that are constantly developing standards for new technologies and updating standards for older products. An open, collaborative community that enhances the competitiveness of U.S. organizations and brings technological advancement to society through the development and promotion of consensus-driven U.S. and global Information Technology standards. More than 2000 standards have been created and approved through

1105-498: Is the second computer in the IBM Personal Computer line, released on March 8, 1983. Except for the addition of a built-in hard drive and extra expansion slots, it is very similar to the original IBM PC model 5150 from 1981. IBM did not specify an expanded form of "XT" on the machine, press releases, brochures or documentation, but some publications expanded the term as " eXtended Technology " or just " eXTended ". The XT

1170-623: The XT/370 ; they had an additional (co-)processor board that could execute System/370 instructions. An XT-based machine with a Series/1 co-processor board existed as well, but it had its own System Unit number, the IBM 4950 . In 1986, the XT 286 (model 5162) was released with a 6 MHz Intel 80286 processor. Despite being marketed as a lower-tier model than the IBM AT , this system runs many applications faster than

1235-493: The Zip drive and SuperDisk drive . Some early ATAPI devices were simply SCSI devices with an ATA/ATAPI to SCSI protocol converter added on. The SCSI commands and responses used by each class of ATAPI device (CD-ROM, tape, etc.) are described in other documents or specifications specific to those device classes and are not within ATA/ATAPI or the T13 committee's purview. One commonly used set

1300-434: The ATA cable. This allows any device class for which a SCSI command set has been defined to be interfaced via ATA/ATAPI. ATAPI devices are also "speaking ATA", as the ATA physical interface and protocol are still being used to send the packets. On the other hand, ATA hard drives and solid state drives do not use ATAPI. ATAPI devices include CD-ROM and DVD-ROM drives, tape drives , and large-capacity floppy drives such as

1365-448: The ATA specifications. A 44-pin variant PATA connector is used for 2.5 inch drives inside laptops. The pins are closer together (2.0 mm pitch) and the connector is physically smaller than the 40-pin connector. The extra pins carry power. ATA's cables have had 40 conductors for most of its history (44 conductors for the smaller form-factor version used for 2.5" drives—the extra four for power), but an 80-conductor version appeared with

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1430-745: The ATA/ATAPI-6 standard (2002). Initially, the size of an ATA drive was stored in the system x86 BIOS using a type number (1 through 45) that predefined the C/H/S parameters and also often the landing zone, in which the drive heads are parked while not in use. Later, a "user definable" format called C/H/S or cylinders, heads, sectors was made available. These numbers were important for the earlier ST-506 interface, but were generally meaningless for ATA—the CHS parameters for later ATA large drives often specified impossibly high numbers of heads or sectors that did not actually define

1495-447: The ATs of the time with 6 MHz 286 processors, since it has zero- wait state RAM. It shipped with 640 KB RAM standard, an AT-style 1.2 MB high-density diskette drive and a 20 MB hard disk. Despite these features, reviews rated it as a poor market value. The XT 286 uses a 157-watt power supply, which can internally switch between 115 or 230 V AC operation. Both

1560-489: The Extender card inserts wait states for memory in the Expansion Unit, so it may be preferable to install memory into the main system unit. The 5161 can be connected to either an XT or to the earlier 5150 (the original IBM PC). PC DOS 2.0 offers a 9-sector floppy disk format, providing 180K/360K (single- vs. dual-sided) capacity per disk, compared to the 160K/320K provided by the 8-sector format of previous releases. The XT

1625-561: The IBM Model M, but in a modified variant that used the XT's keyboard protocol and lacked LEDs). Submodels 267, 277 and 088 had the original keyboard, but 3.5" floppy drives became available and 20MB Seagate ST-225 hard disks in 5.25" half-height size replaced the full-height 10 MB drives. Submodel 788 was the only XT sold with the Color Graphics Adapter as a standard feature. Submodels 568, 588, and 589 were used as basis for

1690-411: The INCITS process, with many more in development. American National Standards are voluntary and serve U.S. interests well because all materially affected stakeholders have the opportunity to work together to create them. INCITS-approved standards only become mandatory when, and if, they are adopted or referenced by the government or when market forces make them imperative. Given the responsibilities and

1755-444: The US and joint ISO / IEC committees worldwide. This provides a mechanism to create standards that will be implemented in many nations. As such, INCITS' Executive Board also serves as ANSI's Technical Advisory Group for ISO/IEC Joint Technical Committee 1. JTC 1 is responsible for International standardization in the field of information technology. INCITS operates through consensus. INCITS

1820-553: The XT. The 3270 PC , a variant of the XT featuring 3270 terminal emulation, was released in October 1983. Submodel 068 and 078, released in 1985, offered dual-floppy configurations without a hard drive as well, and the new Enhanced Graphics Adapter and Professional Graphics Adapter became available as video card options. In 1986, the 256–640 KB motherboard models were launched, which switched to half-height drives. Submodels 268, 278 and 089 came with 101-key keyboards (essentially

1885-497: The bridge was especially simple in case of an ATA connector being located on an ISA interface card. The integrated controller presented the drive to the host computer as an array of 512-byte blocks with a relatively simple command interface. This relieved the mainboard and interface cards in the host computer of the chores of stepping the disk head arm, moving the head arm in and out, and so on, as had to be done with earlier ST-506 and ESDI hard drives. All of these low-level details of

1950-550: The cable. Cable select is controlled by pin 28. The host adapter grounds this pin; if a device sees that the pin is grounded, it becomes the Device 0 (master) device; if it sees that pin 28 is open, the device becomes the Device 1 (slave) device. This setting is usually chosen by a jumper setting on the drive called "cable select", usually marked CS , which is separate from the Device 0/1 setting. If two drives are configured as Device 0 and Device 1 manually, this configuration does not need to correspond to their position on

2015-409: The cable. Pin 28 is only used to let the drives know their position on the cable; it is not used by the host when communicating with the drives. In other words, the manual master/slave setting using jumpers on the drives takes precedence and allows them to be freely placed on either connector of the ribbon cable. With the 40-conductor cable, it was very common to implement cable select by simply cutting

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2080-467: The computer was booted in some other manner without loading the special utility, the invalid BIOS settings would be used and the drive could either be inaccessible or appear to the operating system to be damaged. Later, an extension to the x86 BIOS disk services called the " Enhanced Disk Drive " (EDD) was made available, which makes it possible to address drives as large as 2 sectors. The first drive interface used 22-bit addressing mode which resulted in

2145-413: The computer's BIOS and/or operating system . In most personal computers the drives are often designated as "C:" for the Device 0 and "D:" for the Device 1 referring to one active primary partitions on each. The mode that a device must use is often set by a jumper setting on the device itself, which must be manually set to Device 0 ( Master ) or Device 1 ( Slave ). If there is a single device on

2210-402: The connection cable to the drive. On an IBM PC compatible, CP/M machine, or similar, this was typically a card installed on a motherboard . The interface cards used to connect a parallel ATA drive to, for example, an ISA Slot , are not drive controllers: they are merely bridges between the host bus and the ATA interface . Since the original ATA interface is essentially just a 16-bit ISA bus ,

2275-482: The era have a SATA hard disk and an optical drive connected to PATA. As of 2007, some PC chipsets , for example the Intel ICH10, had removed support for PATA. Motherboard vendors still wishing to offer Parallel ATA with those chipsets must include an additional interface chip. In more recent computers, the Parallel ATA interface is rarely used even if present, as four or more Serial ATA connectors are usually provided on

2340-713: The expenditures associated with U.S. participation in international standards activities, INCITS considers participation as a "P" member of ISO/IEC JTC 1, as a declaration of support for the international committee's technical work. INCITS policy is to adopt as "Identical" American National Standards all ISO/IEC or ISO standards that fall within its program of work, with exceptions as outlined in our procedures. Accordingly, INCITS will adopt as "Identical" American National Standards all ISO/IEC or ISO standards that fall within its program of work. Similarly, INCITS will withdraw any such adopted American National Standard that has been withdrawn as an ISO/IEC or ISO International Standards. INCITS

2405-559: The goal of remaining software compatible with the existing IBM PC hard drive interface. The first such drives appeared internally in Compaq PCs in 1986 and were first separately offered by Conner Peripherals as the CP342 in June 1987. The term Integrated Drive Electronics refers to the drive controller being integrated into the drive, as opposed to a separate controller situated at the other side of

2470-472: The hard drive in question is also expected to provide good throughput for other tasks at the same time, it probably should not be on the same cable as the optical drive. A drive mode called cable select was described as optional in ATA-1 and has come into fairly widespread use with ATA-5 and later. A drive set to "cable select" automatically configures itself as Device 0 or Device 1 , according to its position on

2535-414: The internal physical layout of the drive at all. From the start, and up to ATA-2, every user had to specify explicitly how large every attached drive was. From ATA-2 on, an "identify drive" command was implemented that can be sent and which will return all drive parameters. Owing to a lack of foresight by motherboard manufacturers, the system BIOS was often hobbled by artificial C/H/S size limitations due to

2600-565: The introduction of the UDMA/66 mode. All of the additional conductors in the new cable are grounds , interleaved with the signal conductors to reduce the effects of capacitive coupling between neighboring signal conductors, reducing crosstalk . Capacitive coupling is more of a problem at higher transfer rates, and this change was necessary to enable the 66 megabytes per second (MB/s) transfer rate of UDMA4 to work reliably. The faster UDMA5 and UDMA6 modes also require 80-conductor cables. Though

2665-548: The manufacturer assuming certain values would never exceed a particular numerical maximum. The first of these BIOS limits occurred when ATA drives reached sizes in excess of 504 MiB , because some motherboard BIOSes would not allow C/H/S values above 1024 cylinders, 16 heads, and 63 sectors. Multiplied by 512 bytes per sector, this totals 528 482 304 bytes which, divided by 1 048 576 bytes per MiB , equals 504 MiB (528 MB ). The second of these BIOS limitations occurred at 1024 cylinders , 256 heads , and 63 sectors , and

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2730-442: The mechanical operation of the drive were now handled by the controller on the drive itself. This also eliminated the need to design a single controller that could handle many different types of drives, since the controller could be unique for the drive. The host need only to ask for a particular sector, or block, to be read or written, and either accept the data from the drive or send the data to it. The interface used by these drives

2795-455: The most common and the least expensive interface for this application. It has largely been replaced by SATA in newer systems. The standard was originally conceived as the "AT Bus Attachment", officially called "AT Attachment" and abbreviated "ATA" because its primary feature was a direct connection to the 16-bit ISA bus introduced with the IBM PC/AT . The original ATA specifications published by

2860-546: The motherboard and SATA devices of all types are common. With Western Digital 's withdrawal from the PATA market, hard disk drives with the PATA interface were no longer in production after December 2013 for other than specialty applications. Parallel ATA cables transfer data 16 bits at a time. The traditional cable uses 40-pin female insulation displacement connectors (IDC) attached to a 40- or 80-conductor ribbon cable . Each cable has two or three connectors, one of which plugs into

2925-753: The number of conductors doubled, the number of connector pins and the pinout remain the same as 40-conductor cables, and the external appearance of the connectors is identical. Internally, the connectors are different; the connectors for the 80-conductor cable connect a larger number of ground conductors to the ground pins, while the connectors for the 40-conductor cable connect ground conductors to ground pins one-to-one. 80-conductor cables usually come with three differently colored connectors (blue, black, and gray for controller, master drive, and slave drive respectively) as opposed to uniformly colored 40-conductor cable's connectors (commonly all gray). The gray connector on 80-conductor cables has pin 28 CSEL not connected, making it

2990-688: The original XT and the XT/286 was discontinued in late 1987 after the launch of the IBM Personal System/2 (PS/2) line. The 8086-powered IBM PS/2 Model 30 served as the direct replacement for the XT in that PS/2 line. Unlike higher-end entries in the PS/2 line, which feature the Micro Channel expansion bus, the Model 30 contains 8-bit ISA bus slots, exactly like the XT. The XT was well received, although PC DOS 2.0

3055-408: The other device on the cable, reducing the impact of the "one operation at a time" limit. The impact of this on a system's performance depends on the application. For example, when copying data from an optical drive to a hard drive (such as during software installation), this effect probably will not matter. Such jobs are necessarily limited by the speed of the optical drive no matter where it is. But if

3120-650: The pin 28 wire between the two device connectors; putting the slave Device 1 device at the end of the cable, and the master Device 0 on the middle connector. This arrangement eventually was standardized in later versions. However, it had one drawback: if there is just one master device on a 2-drive cable, using the middle connector, this results in an unused stub of cable, which is undesirable for physical convenience and electrical reasons. The stub causes signal reflections , particularly at higher transfer rates. INCITS The InterNational Committee for Information Technology Standards ( INCITS ), (pronounced "insights"),

3185-416: The primary storage device interface for PCs soon after its introduction. In some systems, a third and fourth motherboard interface was provided, allowing up to eight ATA devices to be attached to the motherboard. Often, these additional connectors were implemented by inexpensive RAID controllers. Soon after the introduction of Serial ATA (SATA) in 2003, use of Parallel ATA declined. Some PCs and laptops of

3250-427: The problem by adding three extra expansion slots for a total of eight. While the slots themselves are identical to those in the original PC, the amount of physical space in the chassis differs, so two of the new slots (located behind the hard drive) cannot accept full-length cards. In addition, the spacing of the slots is narrower than in the original PC, making it impossible to install some multi-board cards. The 5161

3315-472: The same cable. For all modern ATA host adapters, this is not true, as modern ATA host adapters support independent device timing . This allows each device on the cable to transfer data at its own best speed. Even with earlier adapters without independent timing, this effect applies only to the data transfer phase of a read or write operation. This is caused by the omission of both overlapped and queued feature sets from most parallel ATA products. Only one device on

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3380-485: The same time that the ATA-1 standard was adopted, Western Digital introduced drives under a newer name, Enhanced IDE (EIDE). These included most of the features of the forthcoming ATA-2 specification and several additional enhancements. Other manufacturers introduced their own variations of ATA-1 such as "Fast ATA" and "Fast ATA-2". The new version of the ANSI standard, AT Attachment Interface with Extensions ATA-2 (X3.279-1996),

3445-413: The slave position for drives configured cable select. If two devices are attached to a single cable, one must be designated as Device 0 (in the past, commonly designated master ) and the other as Device 1 (in the past, commonly designated as slave ). This distinction is necessary to allow both drives to share the cable without conflict. The Device 0 drive is the drive that usually appears "first" to

3510-467: The standards committees use the name "AT Attachment". The "AT" in the IBM PC/AT referred to "Advanced Technology" so ATA has also been referred to as "Advanced Technology Attachment". When a newer Serial ATA (SATA) was introduced in 2003, the original ATA was renamed to Parallel ATA, or PATA for short. Physical ATA interfaces became a standard component in all PCs, initially on host bus adapters, sometimes on

3575-479: The third-party group MSFN have modified the Windows 98 disk drivers to add unofficial support for 48-bit LBA to Windows 95 OSR2 , Windows 98 , Windows 98 SE and Windows ME . Some 16-bit and 32-bit operating systems supporting LBA48 may still not support disks larger than 2 TiB due to using 32-bit arithmetic only; a limitation also applying to many boot sectors . Parallel ATA (then simply called ATA or IDE) became

3640-402: The two IDE cables, which can have two drives each (primary master, primary slave, secondary master, secondary slave). There are many debates about how much a slow device can impact the performance of a faster device on the same cable. On early ATA host adapters, both devices' data transfers can be constrained to the speed of the slower device, if two devices of different speed capabilities are on

3705-439: The video controller, disk controller and printer interface) each came as separate expansion cards and could quickly fill up all five available slots, requiring the user to swap cards in and out as tasks demanded. Some PC clones addressed this problem by integrating components into the motherboard to free up slots, while peripheral manufacturers produced products which integrated multiple functions into one card. The XT addressed

3770-430: Was approved in 1996. It included most of the features of the manufacturer-specific variants. ATA-2 also was the first to note that devices other than hard drives could be attached to the interface: 3.1.7 Device: Device is a storage peripheral. Traditionally, a device on the ATA interface has been a hard disk drive, but any form of storage device may be placed on the ATA interface provided it adheres to this standard. ATA

3835-418: Was especially written to take advantage of the coprocessor would show a significant speedup. The power supply is 130 watts, an upgrade from the original PC. Those sold in the US were configured for 120 V AC only and could not be used with 240 V mains supplies. XTs with 240 V-compatible power supplies were later sold in international markets. Both were rated at 130 watts. IBM made several submodels of

3900-656: Was established in 1961 as the Accredited Standards Committee X3, Information Technology and is sponsored by Information Technology Industry Council (ITI), a trade association representing providers of information technology products and services then known as the Business Equipment Manufacturers Association (BEMA) and later renamed the Computer and Business Equipment Manufacturers' Association (CBEMA). The first organizational meeting

3965-491: Was in February 1961 with ITI (CBEMA then) taking Secretariat responsibility. X3 was established under American National Standards Institute (ANSI) procedures. The forum was renamed Accredited Standards Committee NCITS, National Committee for Information Technology Standards in 1997, and the current name was approved in 2001. IBM Personal Computer XT The IBM Personal Computer XT (model 5160, often shortened to PC/XT )

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4030-517: Was not offered in a floppy-only model for its first two years on the market, although the standard ribbon cable with two floppy connectors was still included. At that time, in order to get a second floppy drive, the user had to purchase the 5161 expansion chassis. Like the original PC, the XT came with IBM BASIC in ROM . The XT BIOS also displays a memory count during the POST , unlike the original PC. The XT has

4095-469: Was originally designed for, and worked only with, hard disk drives and devices that could emulate them. The introduction of ATAPI (ATA Packet Interface) by a group called the Small Form Factor committee (SFF) allowed ATA to be used for a variety of other devices that require functions beyond those necessary for hard disk drives. For example, any removable media device needs a "media eject" command, and

4160-462: Was regarded as an incremental improvement over the PC and a disappointment compared to the next-generation successor that some had anticipated. Compared to the original IBM PC, the XT has the following major differences: Otherwise the specifications are identical to the original PC. The number of expansion slots in the original IBM PC was a limiting factor for the product, since essential components (such as

4225-501: Was standardized in 1994 as ANSI standard X3.221-1994, AT Attachment Interface for Disk Drives . After later versions of the standard were developed, this became known as "ATA-1". A short-lived, seldom-used implementation of ATA was created for the IBM XT and similar machines that used the 8-bit version of the ISA bus. It has been referred to as "XT-IDE" , "XTA" or "XT Attachment". In 1994, about

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