Buffer To Host Serial Ata

6 Serial ATA Transfer Modes SATA-150 SATA-300 SATA-600 Uses 8B/10B to encode/decode data sent along SATA cable No 4 consecutive 0s No more than six or.

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• In computer storage, disk buffer often ambiguously called disk cache or cache buffer is the embedded memory in a hard disk drive HDD acting as a buffer between.
• 4 Application Note Serial ATA II Native Command Queuing Overview 5 Read FPDMA Queued Command Format.

Our user-friendly serial data switches are versatile, intelligent, and allow for seamless communication between your PC and multiple RS-232 devices.

Not to be confused with page cache.

On this hard disk drive, the controller board contains a RAM integrated circuit used for the disk buffer.

A 500 GB hard disk drive with a 16 MB buffer

In computer storage, disk buffer often ambiguously called disk cache or cache buffer is the embedded memory in a hard disk drive HDD acting as a buffer between the rest of the computer and the physical hard disk platter that is used for storage. 1 Modern hard disk drives come with 8 to 128 MiB of such memory, and solid-state drives come with up to 1 GB of cache memory.

Since the late 1980s, nearly all disks sold have embedded microcontrollers and either an ATA, Serial ATA, SCSI, or Fibre Channel interface. The drive circuitry usually has a small amount of memory, used to store the data going to and coming from the disk platters.

The disk buffer is physically distinct from and is used differently from the page cache typically kept by the operating system in the computer s main memory. The disk buffer is controlled by the microcontroller in the hard disk drive, and the page cache is controlled by the computer to which that disk is attached. The disk buffer is usually quite small, ranging between 8 and 128 MiB, and the page cache is generally all unused main memory. While data in the page cache is reused multiple times, the data in the disk buffer is rarely reused. 2 In this sense, the terms disk cache and cache buffer are misnomers; the embedded controller s memory is more appropriately called disk buffer.

Note that disk array controllers, as opposed to disk controllers, usually have normal cache memory of around 0.5–8 GiB.

When executing a read from the disk, the disk arm moves the read/write head to or near the correct track, and after some settling time the read head begins to pick up bits. Usually, the first sectors to be read are not the ones that have been requested by the operating system. The disk s embedded computer typically saves these unrequested sectors in the disk buffer, in case the operating system requests them later.

The speed of the disk s I/O interface to the computer almost never matches the speed at which the bits are transferred to and from the hard disk platter. The disk buffer is used so that both the I/O interface and the disk read/write head can operate at full speed.

The disk s embedded microcontroller may signal the main computer that a disk write is complete immediately after receiving the write data, before the data are actually written to the platter. This early signal allows the main computer to continue working even though the data has not actually been written yet. This can be somewhat dangerous, because if power is lost before the data are permanently fixed in the magnetic media, the data will be lost from the disk buffer, and the file system on the disk may be left in an inconsistent state.

On some disks, this vulnerable period between signaling the write complete and fixing the data can be arbitrarily long, as the write can be deferred indefinitely by newly arriving requests. For this reason, the use of write acceleration can be controversial. Consistency can be maintained, however, by using a battery-backed memory system for caching data, although this is typically only found in high-end RAID controllers.

Alternatively, the caching can simply be turned off when the integrity of data is deemed more important than write performance. Another option is to send data to disk in a carefully managed order and to issue cache flush commands in the right places, which is usually referred to as the implementation of write barriers.

Newer SATA and most SCSI disks can accept multiple commands while any one command is in operation through command queuing see NCQ and TCQ. These commands are stored by the disk s embedded controller until they are completed. One benefit is that the commands can be re-ordered to be processed more efficiently, so that commands affecting the same area of a disk are grouped together. Should a read reference the data at the destination of a queued write, the to-be-written data will be returned.

NCQ is usually used in combination with enabled write buffering. In case of a read/write FPDMA command with Force Unit Access FUA bit set to 0 and enabled write buffering, an operating system may see the write operation finished before the data is physically written to the media. In case of FUA bit set to 1 and enabled write buffering, write operation returns only after the data is physically written to the media.

Cache control from the host edit

Data that was accepted in write cache of a disk device will be eventually written to disk platters, provided that no starvation condition occurs as a result of firmware flaw, and that disk power supply is not interrupted before cached writes are forced to disk platters. In order to control write cache, ATA specification included FLUSH CACHE E7h and FLUSH CACHE EXT EAh commands. These commands cause the disk to complete writing data from its cache, and disk will return good status after data in the write cache is written to disk media. In addition, flushing the cache can be initiated at least to some disks by issuing Soft reset or Standby Immediate command. 3

Mandatory cache flushing is used in Linux for implementation of write barriers in some filesystems for example, ext4, together with Force Unit Access write command for journal commit blocks. 4

Force Unit Access FUA is an I/O write command option that forces written data all the way to stable storage. 5 FUA write commands WRITE DMA FUA EXT – 3Dh, WRITE DMA QUEUED FUA EXT – 3Eh, WRITE MULTIPLE FUA EXT – CEh, in contrast to corresponding commands without FUA, write data directly to the media, regardless of whether write caching in the device is enabled or not. FUA write command will not return until data is written to media, thus data written by a completed FUA write command is on permanent media even if the device is powered off before issuing a FLUSH CACHE command. 6 7

FUA appeared in the SCSI command set, and was later adopted by SATA with NCQ. FUA is more fine-grained as it allows a single write operation to be forced to stable media and thus has smaller overall performance impact when compared to commands that flush the entire disk cache, such as the ATA FLUSH CACHE family of commands. 7 8

Windows Vista and up supports FUA as part of Transactional NTFS, but only for SCSI or Fibre Channel disks where support for FUA is common. 9 It is not known whether a SATA drive that supports FUA write commands will actually honor the command and write data to disk platters as instructed; citation needed thus, Windows 8 and Windows Server 2012 instead send commands to flush the disk write cache after certain write operations. 10

Although the Linux kernel gained support for NCQ around 2007, SATA FUA remains disabled by default because of regressions that were found in 2012 when the kernel s support for FUA was tested. 11 12 The Linux kernel supports FUA at the block layer level. 13

Mark Kyrnin. What to Look for in a Hard Drive. about.com. Retrieved 2014-12-20. A drive s buffer is an amount of RAM on the drive to store frequently accessed data from the drive.

Charles M. Kozierok 2001-04-17. Internal Cache Buffer Size. pcguide.com. Retrieved 2014-12-20.

Hitachi 2006. Deskstar 7K80 Disk Drive Specification, 4th Edition Revision 1.6 12 September 2006 Final. Hitachi Global Storage Technologies. pp. 99, 130, 131.

Christoph Hellwig; Theodore Ts o. Does ext4 send FUA to flush disk cache. spinics.net. Retrieved 2014-03-18.

Jonathan Corbet 2010-08-18. The end of block barriers. LWN.net. Retrieved 2015-06-27.

Information technology-AT Attachment 8 - ATA/ATAPI Command Set ATA8-ACS PDF. T13/1699-D, revision 6-a, 2008-09-06. American National Standards Institute, Inc. Retrieved 2014-03-18.

a b Gregory Smith 2010. PostgreSQL 9.0: High Performance. Packt Publishing Ltd. p. 78. ISBN 978-1-84951-031-8.

Bruce Jacob; Spencer Ng; David Wang 2010. Memory Systems: Cache, DRAM, Disk. Morgan Kaufmann. p. 734. ISBN 978-0-08-055384-9.

Deploying Transactional NTFS Windows. Msdn.microsoft.com. 2013-12-05. Retrieved 2014-01-24.

Forced Unit Access Working Hard In IT. Workinghardinit.wordpress.com. 2012-10-12. Retrieved 2014-01-24.

Storage related regression in linux-next 20120824. 2012-09-12. Retrieved 2015-06-27.

Revert libata: enable SATA disk fua detection on default. 2012-09-13. Retrieved 2015-06-27.

Linux kernel documentation: Documentation/block/writeback_cache_control.txt. kernel.org. 2013-08-12. Retrieved 2014-01-24.

Retrieved from https://en.wikipedia.org/w/index.php.title Disk_buffer oldid 684901263

Categories: Computer storage devicesHard disk computer storage.

Type: Internal storage device connector: Production history; Designer: Western Digital, subsequently amended by many others: Designed: 1986: Superseded by: Serial ATA.

Parallel ATA PATA, originally AT Attachment, is an interface standard for the connection of storage devices such as hard disk drives, floppy disk drives, and optical disc drives in computers. The standard is maintained by the X3/INCITS committee. 1 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 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 Serial ATA SATA in 2003, the original ATA was renamed to Parallel ATA, or PATA for short.

Parallel ATA cables have a maximum allowable length of only 18 in 457 mm. 2 3 Because of this limit, the technology normally appears as an internal computer storage interface. For many years, ATA provided the most common and the least expensive interface for this application. It has largely been replaced by SATA in newer systems.

1.9 Interface size limitations

2.1 Differences between connectors on 80-conductor cables

2.2 Multiple devices on a cable

2.3.1 Master and slave clarification

2.4 Serialized, overlapped, and queued operations

2.5 Two devices on one cable speed impact

2.6 HDD passwords and security

2.7 External parallel ATA devices

4 ATA standards versions, transfer rates, and features

4.1 Features introduced with each ATA revision

4.2 Speed of defined transfer modes

5 Related standards, features, and proposals

5.1 ATAPI Removable Media Device ARMD

The PATA standard was originally conceived as the PC/AT Attachment because its primary feature was a direct connection to the 16-bit ISA bus introduced with the IBM PC/AT. 4 The AT in IBM PC/AT refers to Advanced Technology, but the ATA specifications simply use the name AT Attachment, to avoid possible trademark issues with IBM.

Example of a 1992 80386 PC motherboard with nothing built in other than memory, keyboard, processor, cache, realtime clock, and slots. Such basic motherboards could have been outfitted with either the ST-506 or ATA interface, but usually not both. A single 2-drive ATA interface and a floppy interface was added to this system via the 16-bit ISA card.

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 Control Data Corporation who manufactured the hard drive part and Compaq Computer into whose systems these drives would initially go, they developed the connector, the signaling protocols and so on, with the goal of remaining software compatible with the existing ST-506 hard drive interface. 5 The first such drives appeared in Compaq PCs in 1986. 6 7

The term Integrated Drive Electronics refers not just to the connector and interface definition, but also to the fact that the drive controller is integrated into the drive, as opposed to a separate controller on or connected to the motherboard. The interface cards used to connect a parallel ATA drive to, for example, a PCI 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 in disguise, 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 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 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 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. 8 9

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. 10

An Oak Technology Mozart 16 16-bit ISA sound card, from when the CDROM drive interface had not yet been standardized. This card offers four separate interface connectors for IDE, Panasonic, Mitsumi, and Sony CDROM drives, but only one connector could be used since they all shared the same interface wiring.

A SoundBlaster 32 16-bit ISA sound card, from after connector standardization had occurred, with just an IDE interface for the CDROM drive.

When PC motherboard makers started to include onboard ATA interfaces in place of the earlier ISA plug-in cards, there was usually only one ATA connector on the board, which could support up to two hard drives. At the time, in combination with the floppy drive, this was sufficient for most people. When the CD-ROM was developed, many computers would have been unable to accept these drives if they had been ATA devices, due to already having two hard drives installed. Adding the CD-ROM drive would have required removal of one of the drives. dubious – discuss

SCSI was available as a CD-ROM expansion option at the time, but devices with SCSI were more expensive than ATA devices due to the need for a smart interface that is capable of bus arbitration. SCSI typically added US 100–300 to the cost of a storage device, in addition to the cost of a SCSI host adapter.

The less expensive solution was the addition of a dedicated CD-ROM interface, which was typically included as an expansion option on a sound card. PC motherboards initially did not come with support for more than simple beeps from internal speakers; thus, sound cards such as the Sound Blaster Pro were available for use with games, operating system and software event sounds, or to listen to audio CDs. Also, sound cards commonly included a gameport joystick/gamepad port along with interfaces to control a CD-ROM and transmit CD audio to the system.

Initially, the second drive interface was not well defined. It was first introduced with interfaces specific to certain CD-ROM drives such as Mitsumi, Sony or Panasonic drives, 11 and it was common to find early sound cards with two or three separate connectors each designed to match a certain brand of CD-ROM drive. This evolved into the standard ATA interface for ease of cross-compatibility, though the sound card ATA interface still usually supported only a single CD-ROM and not hard drives.

This second ATA interface on the sound card eventually evolved into the second motherboard ATA interface which was long included as a standard component in all PCs. Called the primary and secondary ATA interfaces, they were assigned to base addresses 0x1F0 and 0x170 on ISA bus systems.

In 1994, about 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, was approved in 1996. It included most of the features of the manufacturer-specific variants. 12 13

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.

AT Attachment Interface with Extensions ATA-2, page 2 13

Main article: ATA Packet Interface

As mentioned in the previous sections, ATA 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 a way for the host to determine whether the media is present, and these were not provided in the ATA protocol.

The Small Form Factor committee approached this problem by defining ATAPI, the ATA Packet Interface. ATAPI is actually 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. In fact, some early ATAPI devices were simply SCSI devices with an ATA/ATAPI to SCSI protocol converter added on. The SCSI commands and responses are embedded in packets hence ATA Packet Interface for transmission on 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 the Zip drive and SuperDisk drive.

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 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. 14 15 16

The ATA/ATAPI-4 standard also introduced several Ultra DMA transfer modes. These initially supported speeds from 16 MByte/s to 33 MByte/second. 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 MByte/s.

Ultra ATA, abbreviated UATA, 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. 17 Most of Western Digital s changes, along with others, were included in the ATA/ATAPI-6 standard 2002.

The terms integrated drive electronics IDE, enhanced IDE and EIDE have come to be used interchangeably with ATA now Parallel ATA, or PATA.

In addition, there have been several generations of EIDE drives marketed, compliant with various versions of the ATA specification. An early EIDE drive might be compatible with ATA-2, while a later one with ATA-6.

Nevertheless, a request for an IDE or EIDE drive from a computer parts vendor will almost always yield a drive that will work with most Parallel ATA interfaces.

Another common usage is to refer to the specification version by the fastest mode supported. For example, ATA-4 supported Ultra DMA modes 0 through 2, the latter providing a maximum transfer rate of 33 megabytes per second. ATA-4 drives are thus sometimes called UDMA-33 drives, and sometimes ATA-33 drives. Similarly, ATA-6 introduced a maximum transfer speed of 100 megabytes per second, and some drives complying to this version of the standard are marketed as PATA/100 drives.

x86 BIOS size limitations edit

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 18 and also often the landing zone, in which the drive heads are parked while not in use. Later, a user definable format 18 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 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 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 megabytes, 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 528482304 bytes which, divided by 1048576 bytes per megabyte, equals 504 megabytes.

The second of these BIOS limitations occurred at 1024 cylinders, 256 heads, and 63 sectors, and a bug in MS-DOS and MS-Windows 95 limited the number of heads to 255. This totals to 8422686720 bytes, 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 tiny 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 new large hard drives to help overcome these problems. However, if 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 264 sectors. 19

Interface size limitations edit

The first drive interface used 22-bit addressing mode which resulted in 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 228 268435456 sectors blocks of 512 bytes each, resulting in a maximum capacity of 128 GiB 137 GB. 20

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 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-SP 1, and Windows 2000 pre-SP 3, 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. 21

Older operating systems, such as Windows 98, do not support 48-bit LBA at all. However, members of the third-party group MSFN 22 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 arithmetics only; a limitation also applying to many boot sectors.

Parallel ATA then simply called ATA or IDE became 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. The first motherboards with built-in SATA interfaces usually had only a single PATA connector for up to two PATA devices, along with multiple SATA connectors.

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 the motherboard and SATA devices of all types are common.

With Western Digital s withdrawal from the market, hard disk drives with the PATA interface will no longer be in production after December 2013 for other than specialty applications. 23

Parallel ATA cables transfer data 16 bits at a time. The traditional cable uses 40-pin connectors attached to a ribbon cable. Each cable has two or three connectors, one of which plugs into an 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.

ATA s cables have had 40 wires 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-wire version appeared with the introduction of the Ultra DMA/33 UDMA mode. All of the additional wires in the new cable are ground wires, interleaved with the previously defined wires to reduce the effects of capacitive coupling between neighboring signal wires, 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.

ATA cables: 40-wire ribbon cable top, and 80-wire ribbon cable bottom

Though the number of wires 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-wire cable connect a larger number of ground wires to the ground pins, while the connectors for the 40-wire cable connect ground wires to ground pins one-for-one. 80-wire 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-wire cable s connectors commonly all gray. The gray connector on 80-conductor cables has pin 28 CSEL not connected, making it the slave position for drives configured cable select.

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 the ATA specifications.

In the ATA standard, pin 20 is defined as mechanical key and is not used. This socket on the female connector is often obstructed, requiring pin 20 to be omitted from the male cable or drive connector, making it impossible to plug it in the wrong way round; a male connector with pin 20 present cannot be used. However, some flash memory drives can use pin 20 as VCC_in to power the drive without requiring a special power cable; this feature can only be used if the equipment supports this use of pin 20. 24

Pin 28 of the gray slave/middle connector of an 80-conductor cable is not attached to any conductor of the cable. It is attached normally on the black master drive end and blue motherboard end connectors.

Pin 34 is connected to ground inside the blue connector of an 80-conductor cable but not attached to any conductor of the cable. It is attached normally on the gray and black connectors. 25

Differences between connectors on 80-conductor cables edit

Differences between connectors

The image on the right shows PATA connectors after removal of strain relief, cover, and cable. Pin one is at bottom left of the connectors, pin 2 is top left, etc., except that the lower image of the blue connector shows the view from the opposite side, and pin one is at top right.

The connector is an insulation-displacement connector in other words, each contact comprises a pair of points which together pierce the insulation of the ribbon cable with such precision that they make a connection to the desired conductor without harming the insulation on the neighboring wires. The center row of contacts are all connected to the common ground bus and attached to the odd numbered conductors of the cable. The top row of contacts are the even-numbered sockets of the connector mating with the even-numbered pins of the receptacle and attach to every other even-numbered conductor of the cable. The bottom row of contacts are the odd-numbered sockets of the connector mating with the odd-numbered pins of the receptacle and attach to the remaining even-numbered conductors of the cable.

Note the connections to the common ground bus from sockets 2 top left, 19 center bottom row, 22, 24, 26, 30, and 40 on all connectors. Also note enlarged detail, bottom, looking from the opposite side of the connector that socket 34 of the blue connector does not contact any conductor but unlike socket 34 of the other two connectors, it does connect to the common ground bus. On the gray connector, note that socket 28 is completely missing, so that pin 28 of the drive attached to the gray connector will be open. On the black connector, sockets 28 and 34 are completely normal, so that pins 28 and 34 of the drive attached to the black connector will be connected to the cable. Pin 28 of the black drive reaches pin 28 of the host receptacle but not pin 28 of the gray drive, while pin 34 of the black drive reaches pin 34 of the gray drive but not pin 34 of the host. Instead, pin 34 of the host is grounded.

The standard dictates color-coded connectors for easy identification by both installer and cable maker. All three connectors are different from one another. The blue host connector has the socket for pin 34 connected to ground inside the connector but not attached to any conductor of the cable. Since the old 40 conductor cables do not ground pin 34, the presence of a ground connection indicates that an 80 conductor cable is installed. The wire for pin 34 is attached normally on the other types and is not grounded. Installing the cable backwards with the black connector on the system board, the blue connector on the remote device and the gray connector on the center device will ground pin 34 of the remote device and connect host pin 34 through to pin 34 of the center device. The gray center connector omits the connection to pin 28 but connects pin 34 normally, while the black end connector connects both pins 28 and 34 normally.

Multiple devices on a cable edit

If two devices are attached to a single cable, one must be designated as device 0 commonly referred to as master and the other as device 1 slave. This distinction is necessary to allow both drives to share the cable without conflict. The master drive is the drive that usually appears first to the computer s BIOS and/or operating system. On old BIOSes Intel 486 era and older, the drives are often referred to by the BIOS as C for the master and D for the slave following the way DOS would refer to the active primary partitions on each.

The mode that a drive must use is often set by a jumper setting on the drive itself, which must be manually set to master or slave. If there is a single device on a cable, it should be configured as master. However, some hard 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 slave drive most often seen where an optical drive is the only device on the secondary ATA interface.

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 master or slave, according to its position on 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 master device; if it sees that pin 28 is open, the device becomes the 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 master or slave setting.

Note that if two drives are configured as master and slave manually, this configuration does not need to correspond to their position on 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.

With the 40-wire cable, it was very common to implement cable select by simply cutting the pin 28 wire between the two device connectors; putting the slave device at the end of the cable, and the master on the middle connector. This arrangement eventually was standardized in later versions. If there is just one device on the cable, 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.

Starting with the 80-wire cable defined for use in ATAPI5/UDMA4, the master device goes at the end of the 18-inch 460 mm cable the black connector and the slave device goes on the middle connector the gray one and the blue connector goes onto the motherboard. So, if there is only one master device on the cable, there is no cable stub to cause reflections. Also, cable select is now implemented in the slave device connector, usually simply by omitting the contact from the connector body.

Master and slave clarification edit

Although they are in extremely common use, the terms master and slave do not actually appear in current versions of the ATA specifications. The two devices are simply referred to as device 0 and device 1, respectively, in ATA-2 and later.

It is a common myth that the controller on the master drive assumes control over the slave drive, or that the master drive may claim priority of communication over the other device on the same ATA interface. In fact, the drivers in the host operating system perform the necessary arbitration and serialization, and each drive s onboard controller operates independently of the other.

Serialized, overlapped, and queued operations edit

The parallel ATA protocols up through ATA-3 require that once a command has been given on an ATA interface, it must complete before any subsequent command may be given. Operations on the devices must be serialized with only one operation in progress at a time with respect to the ATA host interface. A useful mental model is that the host ATA interface is busy with the first request for its entire duration, and therefore can not be told about another request until the first one is complete. The function of serializing requests to the interface is usually performed by a device driver in the host operating system.

The ATA-4 and subsequent versions of the specification have included an overlapped feature set and a queued feature set as optional features, both being given the name Tagged Command Queuing, a reference to a set of features from SCSI which the ATA version attempts to emulate. However, support for these is extremely rare in actual parallel ATA products and device drivers because these feature sets were implemented in such a way as to maintain software compatibility with its heritage as originally an extension of the ISA bus. This implementation resulted in excessive CPU utilization which largely negated the advantages of command queuing. By contrast, overlapped and queued operations have been common in other storage buses, in particular, SCSI s version of tagged command queuing had no need to be software compatible with ISA s APIs, allowing it to attain high performance with low overhead on buses which supported first party DMA like PCI. This has long been seen as a major advantage of SCSI.

The Serial ATA standard has supported native command queueing since its first release, but it is an optional feature for both host adapters and target devices. Many less expensive PC motherboards do not support NCQ. Many SATA/II hard drives sold today support NCQ, while no removable CD/DVD drives do because the ATAPI command set used to control them prohibits queued operations.

Two devices on one cable speed impact edit

There are many debates about how much a slow device can impact the performance of a faster device on the same cable. There is an effect, but the debate is confused by the blurring of two quite different causes, called here Lowest speed and One operation at a time.

It is a common misconception that, if two devices of different speed capabilities are on the same cable, both devices data transfers will be constrained to the speed of the slower device.

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 older adapters without independent timing, this effect applies only to the data transfer phase of a read or write operation. This is usually the shortest part of a complete read or write operation. 26

This is caused by the omission of both overlapped and queued feature sets from most parallel ATA products. Only one device on 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 its onboard cache memory, before the data is written to the slow magnetic storage. This allows commands to be sent to 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 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.

HDD passwords and security edit

ATA Secure Erase redirects here. For ATA Secure Erase with flash memory, see Write amplification Secure erase. For general use, see Disk formatting Recovery of data from a formatted disk.

The disk lock is a built-in security feature in the disk. It is part of the ATA specification, and thus not specific to any brand or device. The disk lock can be enabled and disabled by sending special ATA commands to the drive. If a disk is locked, it will refuse all access until it is unlocked.

A disk always has two passwords: A User password and a Master password. Most disks support a Master Password Revision Code. Reportedly, citation needed some disks can report if the Master password has been changed, or if it still is the factory default. The revision code is word 92 in the IDENTIFY response. Reportedly, citation needed on some disks, a value of 0xFFFE means the Master password is unchanged. The standard does not distinguish this value.

A disk can be locked in two modes: High security mode or Maximum security mode. Bit 8 in word 128 of the IDENTIFY response shows which mode the disk is in: 0 High, 1 Maximum.

In High security mode, the disk can be unlocked with either the User or Master password, using the SECURITY UNLOCK DEVICE ATA command. There is an attempt limit, normally set to 5, after which the disk must be power cycled or hard-reset before unlocking can be attempted again. Also in High security mode, the SECURITY ERASE UNIT command can be used with either the User or Master password.

In Maximum security mode, the disk can be unlocked only with the User password. If the User password is not available, the only remaining way to get at least the bare hardware back to a usable state is to issue the SECURITY ERASE PREPARE command, immediately followed by SECURITY ERASE UNIT. In Maximum security mode, the SECURITY ERASE UNIT command requires the Master password and will completely erase all data on the disk. The operation is slow. It may take half an hour or more, depending on the size of the disk. Word 89 in the IDENTIFY response indicates how long the operation will take. 27

While the ATA disk lock is intended to be impossible to defeat without a valid password, there are workarounds to unlock a drive. Many data recovery companies offer unlocking services, 28 so while the disk lock will deter a casual attacker, it is not secure against a qualified adversary.

External parallel ATA devices edit

It is extremely uncommon to find external PATA devices that directly use the interface for connection to a computer. PATA is primarily restricted to devices installed internally, due to the short data cable specification. A device connected externally needs additional cable length to form a U-shaped bend so that the external device may be placed alongside, or on top of the computer case, and the standard cable length is too short to permit this.

For ease of reach from motherboard to device, the connectors tend to be positioned towards the front edge of motherboards, for connection to devices protruding from the front of the computer case. This front-edge position makes extension out the back to an external device even more difficult. Ribbon cables are poorly shielded, and the standard relies upon the cabling to be installed inside a shielded computer case to meet RF emissions limits.

All external PATA devices, such as external hard drives, use some other interface technology to bridge the distance between the external device and the computer. USB is the most common external interface, followed by Firewire. A bridge chip inside the external devices converts from the USB interface to PATA, and typically only supports a single external device without cable select or master/slave.

Compact flash is just a miniature ATA interface, slightly modified to be able to also supply power to the CF device.

Compact Flash in its IDE mode is essentially just a miniaturized ATA interface, intended for use on devices that use flash memory storage. No interfacing chips or circuitry are required, other than to directly adapt the smaller CF socket onto the larger ATA connector.

The ATA connector specification does not include pins for supplying power to a CF device, so power is inserted into the connector from a separate source. The exception to this is when the CF device is connected to a 44-pin ATA bus designed for 2.5-inch hard disk drives, commonly found in notebook computers, as this bus implementation must provide power to a standard hard disk drive.

CF devices can be designated as master or slave on an ATA interface, though since most CF devices offer only a single socket, it is not necessary to offer this selection to end users. Although CF can be hot-pluggable with additional design methods, by default when wired directly to an ATA interface, it is not intended to be hot-pluggable.

ATA standards versions, transfer rates, and features edit

The following table shows the names of the versions of the ATA standards and the transfer modes and rates supported by each. Note that the transfer rate for each mode for example, 66.7 MB/s for UDMA4, commonly called Ultra-DMA 66, defined by ATA-5 gives its maximum theoretical transfer rate on the cable. This is simply two bytes multiplied by the effective clock rate, and presumes that every clock cycle is used to transfer end-user data. In practice, of course, protocol overhead reduces this value.

Congestion on the host bus to which the ATA adapter is attached may also limit the maximum burst transfer rate. For example, the maximum data transfer rate for conventional PCI bus is 133 MB/s, and this is shared among all active devices on the bus.

In addition, no ATA hard drives existed in 2005 that were capable of measured sustained transfer rates of above 80 MB/s. Furthermore, sustained transfer rate tests do not give realistic throughput expectations for most workloads: They use I/O loads specifically designed to encounter almost no delays from seek time or rotational latency. Hard drive performance under most workloads is limited first and second by those two factors; the transfer rate on the bus is a distant third in importance. Therefore, transfer speed limits above 66 MB/s really affect performance only when the hard drive can satisfy all I/O requests by reading from its internal cache a very unusual situation, especially considering that such data is usually already buffered by the operating system.

As of April 2010 update, mechanical hard disk drives can transfer data at up to 157 MB/s, 29 which is beyond the capabilities of the PATA/133 specification. High-performance solid state drives can transfer data at up to 308 MB/s. 30

Only the Ultra DMA modes use CRC to detect errors in data transfer between the controller and drive. This is a 16-bit CRC, and it is used for data blocks only. Transmission of command and status blocks do not use the fast signaling methods that would necessitate CRC. For comparison, in Serial ATA, 32-bit CRC is used for both commands and data. 31

Features introduced with each ATA revision edit

22-bit logical block addressing LBA

28-bit logical block addressing LBA

EIDE, Fast ATA, Fast IDE, Ultra ATA

PCMCIA connector. Identify drive command. 32

Single-word DMA modes dropped 33

S.M.A.R.T., Security, 44 pin connector for 2.5 drives

AT Attachment Packet Interface ATAPI support for CD-ROM, tape drives etc., Optional overlapped and queued command set features, Host Protected Area HPA, CompactFlash Association CFA feature set for solid state drives

80-wire cables; CompactFlash connector

48-bit LBA, Device Configuration Overlay DCO,

Automatic Acoustic Management AAM

SATA 1.0, Streaming feature set, long logical/physical sector feature set for non-packet devices

NCITS 397-2005 vol 1 NCITS 397-2005 vol 2 NCITS 397-2005 vol 3

Hybrid drive featuring non-volatile cache to speed up critical OS files

Data Set Management, Extended Power Conditions, CFast, additional stats., etc.

Speed of defined transfer modes edit

Related standards, features, and proposals edit

ATAPI Removable Media Device ARMD edit

ATAPI devices with removable media, other than CD and DVD drives, are classified as ARMD ATAPI Removable Media Device and can appear as either a super-floppy non-partitioned media or a hard drive partitioned media to the operating system. These can be supported as bootable devices by a BIOS complying with the ATAPI Removable Media Device BIOS Specification, 38 originally developed by Compaq Computer Corporation and Phoenix Technologies. It specifies provisions in the BIOS of a personal computer to allow the computer to be bootstrapped from devices such as Zip drives, Jaz drives, SuperDisk LS-120 drives, and similar devices.

These devices have removable media like floppy disk drives, but capacities more commensurate with hard drives, and programming requirements unlike either. Due to limitations in the floppy controller interface most of these devices were ATAPI devices, connected to one of the host computer s ATA interfaces, similarly to a hard drive or CD-ROM device. However, existing BIOS standards did not support these devices. An ARMD-compliant BIOS allows these devices to be booted from and used under the operating system without requiring device-specific code in the OS.

A BIOS implementing ARMD allows the user to include ARMD devices in the boot search order. Usually an ARMD device is configured earlier in the boot order than the hard drive. Similarly to a floppy drive, if bootable media is present in the ARMD drive, the BIOS will boot from it; if not, the BIOS will continue in the search order, usually with the hard drive last.

There are two variants of ARMD, ARMD-FDD and ARMD-HDD. Originally ARMD caused the devices to appear as a sort of very large floppy drive, either the primary floppy drive device 00h or the secondary device 01h. Some operating systems required code changes to support floppy disks with capacities far larger than any standard floppy disk drive. Also, standard-floppy disk drive emulation proved to be unsuitable for certain high-capacity floppy disk drives such as Iomega Zip drives. Later the ARMD-HDD, ARMD- Hard disk device, variant was developed to address these issues. Under ARMD-HDD, an ARMD device appears to the BIOS and the operating system as a hard drive.

In August 2004, Sam Hopkins and Brantley Coile of Coraid specified a lightweight ATA over Ethernet protocol to carry ATA commands over Ethernet instead of directly connecting them to a PATA host adapter. This permitted the established block protocol to be reused in storage area network SAN applications.

Advanced Host Controller Interface AHCI

CE-ATA Consumer Electronics CE ATA

SCSI Small Computer System Interface

BIOS for BIOS Boot Specification BBS

INT 13H for BIOS Enhanced Disk Drive Specification SFF-8039i

IT8212, a low-end Parallel ATA controller

Serial ATA: A Comparison with Ultra ATA Technology PDF. Seagate Technology. Archived from the original PDF on 2012-01-05. Retrieved 23 January 2012.

Frawley, Lucas. Parallel vs. Serial ATA. What Is. The Information for Your Computer Questions. Directron.com. Retrieved 23 January 2012.

Ref - Overview of the IDE/ATA Interface. PCGuide. Retrieved 2013-06-14.

System Architecture: a look at hard drives. Archived from the original on 2010-11-18. Retrieved 2008-07-25. IDE drives on-board controllers are configured to appear to the computer like standard ST506 drives

Charles M. Kozierok 2001-04-17. The PC Guide: Overview and History of the IDE/ATA Interface. Retrieved 2008-08-23.

Gene Milligan 2005-12-18. The History of CAM ATA. Archived from the original on 2010-11-18. Retrieved 2008-08-27.

Charles M. Kozierok 2001-04-17. The PC Guide: ATA ATA-1. Retrieved 2008-08-23.

Technical Committee T13 AT Attachment 1994. AT Attachment Interface for Disk Drives ATA-1. Global Engineering Documents.

Independent Technology Service 2008. Data Recovery and Hard Disk Drive Glossary of Terms. Retrieved 2011-03-11.

Creative Labs sound card documentation showing diagram with custom Mitsumi, Sony, and Panasonic CD-ROM drive connectors

Charles M. Kozierok 2001-04-17. The PC Guide: ATA ATA-2. Retrieved 2008-08-23.

a b Technical Committee T13 AT Attachment 1996. AT Attachment Interface with Extensions ATA-2. Global Engineering Documents.

Charles M. Kozierok 2001-04-17. The PC Guide: SFF-8020 / ATA Packet Interface ATAPI. Retrieved 2008-08-23.

Charles M. Kozierok 2001-04-17. The PC Guide: ATA/ATAPI-4. Retrieved 2008-08-23.

Technical Committee T13 AT Attachment 1998. AT Attachment with Packet Interface Extension ATA/ATAPI-4. Global Engineering Documents.

Western Digital Corporation. Ultra ATA/100 Extends Existing Technology While Increasing Performance and Data Integrity PDF.

a b kursk.ru – Standard CMOS Setup

teleport.com – Interrupts Page

Disk-based memory hard drives, solid state disk devices such as USB drives, DVD-based storage, bit rates, bus speeds, and network speeds, are specified using decimal meanings for K 10001, M 10002, G 10003,

FryeWare 2005. EnableBigLba Registry Setting in Windows 2000 and XP. Retrieved 2011-12-29.  The setting is HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Services atapi Parameters EnableBigLba 1.

LLXX 2006-07-12. Enable48BitLBA - Break the 137 GB barrier.. 1.1. Retrieved 2013-09-03.

Western Digital stops sales of PATA drives. Myce.com. 2013-12-20. Retrieved 2013-12-25.

Information Technology - AT Attachment with Packet Interface - 5 ATA/ATAPI-5 - Working Draft PDF. 2000-02-29. p. 315. Retrieved 2013-08-25.

Charles M. Kozierok 2001-04-17. Independent Master/Slave Device Timing. The PC Guide. Retrieved 2008-08-08.

Rockbox – Unlocking a password protected harddisk

Hard Drive Passwords Easily Defeated; the Truth about Data Protection. wwpi.com. 2007-09-10. Retrieved 2015-08-19.

Patrick Schmid and Achim Roos 2010-04-06. VelociRaptor Returns: 6Gb/s, 600GB, And 10,000 RPM. tomshardware.com. Archived from the original on 2010-11-18. Retrieved 2010-06-26.

Patrick Schmid and Achim Roos 2010-04-13. Spring 2010 Solid State Drive Roundup, Part 2. tomshardware.com. Archived from the original on 2010-11-18. Retrieved 2010-06-26.

Serial ATA A Comparison with Ultra ATA Technology PDF. Archived from the original PDF on 2007-12-03.  www.serialata.org

mpcclub.com – Em8550datasheet.pdf

Direct Memory Access DMA Modes and Bus Mastering DMA

ATA-8 standard working draft T13/1697-D rev. 4 PDF. 2010-06-23.

ATA/ATAPI Command Set - 2 ACS-2 working draft T13/2015-D rev. 6 PDF. 2011-02-22.

Curtis E. Stevens; Paul J. Broyles 1997-01-30. ATAPI Removable Media Device BIOS Specification, Version 1.0 PDF. phoenix.com. Archived from the original PDF on 2010-01-02. Retrieved 2015-08-25.

Retrieved from https://en.wikipedia.org/w/index.php.title Parallel_ATA oldid 700088628 IDE_and_ATA-1

Categories: AT AttachmentComputer storage busesComputer connectors.

2 Barracuda 7200.11 Serial ATA Product Manual, Rev. E 1.1 About the Serial ATA interface The Serial ATA interface provides several advantages over the traditional.

EXtensible Host Controller Interface Revision 1.1 4 Contributors Randy Aull Microsoft Corporation Paul Baleme Intel Corporation Dustin Bingham Intel Corporation.

2 Barracuda 7200.11 Serial ATA Product Manual, Rev. G 1.1 About the Serial ATA interface The Serial ATA interface provides several advantages over the traditional.