IDE (ATA) Bus

Integrated Drive Electronics (Advanced Technology Attachment)

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IDE / ATA Parallel Bus Description

Nominally called the IDE (Integrated Drive Electronics) bus; how ever it's more correctly known as the ATA (Advanced Technology Attachment) specification [ATA Bus]. The IDE bus is used in Personal Computers [PCs] as a hard-drive or peripheral bus to interconnect the PC mother board and a hard drive. The IDE bus is a Parallel bus. With the introduction of the Serial ATA [SATA] specification Parallel ATA [IDE] is now being called PATA.

The specification has been up-graded a number of times each building on the past specification. ATA-1 and 2 were single documents, but like SCSI, after ATA-2 the specification was divided into a number of different documents. Most maintain backward compatibility, keeping in mind the cable changed. Each new version of the standard produced an increase in bus speed. The data transfer rate is shown after each version listed below. The maximum IDE bus speed is 133MBytes/sec [133MBps].

Data is passed Single-Ended via data line and ground. Only the 40 pin connector pin out are referenced below, which are used on 3.5-inch drives, but there is also a 50 pin connector used on 2.5-inch drives. The 50 pin connector adds the power and Master/Slave functions. PCMCIA uses a 68 pin connector. A graph showing the difference between ATA and Ultra ATA timing is shown on the below. The standard defines a single Host or adaptor which connects to one [device 0] or two [device 1] devices in a daisy chained configuration. The IDE, ATA connector pinout is listed in the table below. Note; there is text to decode the 80 pin cable onto the 40-pin connector.

There are a number of versions of the ATA bus, with each of the different versions listed below. The Serial ATA: which replaced the ATA bus is listed on its own page. Details for each bus version are listed below. A graphic which provides a comparison of all the different IDE interfaces listed here is provided on the HardDrive Interface Speed page.

ATA-1 (IDE), [Obsolete] 8.3MBytes/sec, 8 or 16 bit data width, 40 pin data ribbon cable/connector. With a maximum of 2 devices on the bus. Using PIO Modes 0, 1 or 2. Performed no bus error correction. The ATA-1 specification was released in 1994, and was withdrawn in 1999.

ATA-2 (EIDE, or Fast ATA), [Obsolete] 16.6MBytes/sec, 8 or 16 bit data width, 40 pin data ribbon cable/connector. With a maximum of 4 devices on the bus. Using PIO Modes 0, 1, 2, 3, or 4. The ATA-2 specification was released in 1995 and was withdrawn in 2001.

ATA-3, 16MBytes/sec, 16 bit data width, 40 pin data ribbon cable/connector. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2. Runs with 120nS Strobes (rising edge to rising edge). Includes CRC.
ATAPI (ATA Packet Interface) is the CD-ROM side of the interface. It uses the same connector as ATA, and adds 1 for analog and 1 for digital audio. The ATA-3 specification was released in 1997 and was withdrawn in 2002.

ATA-4 Ultra-ATA/33, 33MBytes/sec, 16 bit data width, 40 pin data ribbon cable/connector. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2 and Ultra DMA modes 0, 1, and 2. Runs with 120nS Strobes (rising edge to rising edge), but used both edges of the Strobe producing an effective 60nS Strobe rate. 33MBps Transfer speed = [(1/120nS) x 2 bytes x 2]. Where 120nS cycle time is 4 clock periods at 30nS each. Added CRC checking. The ATA-4 standard was released in 1998.

ATA-5 Ultra-ATA/66, 66MBytes/sec, 16 bit data width 40 pin data connector/80 pin cable, with the additional 40 new pins being Ground. The new cable allows ATA/66 to run at a faster rate then ATA/33. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2 and Ultra DMA modes 0, 1, 2, 3 and 4. Runs with 60nS Strobes (rising edge to rising edge), but uses both edges of the Strobe producing an effective 30nS Strobe rate. 66MBps Transfer speed = [(1/60nS) x 2 bytes x 2]. Where 60nS cycle time is 2 clock periods at 30nS each. The ATA-5 standard was released in 2000.

ATA-6 Ultra-ATA/100, 100MBytes/sec,16 bit data width 40 pin data connector/80 pin cable, with the additional 40 new pins being Ground. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 1 and 2 and Ultra DMA modes 0, 1, 2, 3, 4 and 5. 100MBps Transfer speed = [(1/40nS) x 2 bytes x 2]. Where 40nS cycle time is 2 clock periods at 20nS each. The ATA-6 standard was released in 2002.

ATA-7 Ultra-ATA/133, 133MBytes/sec,16 bit data width 40 pin data connector/80 pin cable, with the additional 40 new pins being Ground. Using PIO Modes 0, 1, 2, 3, or 4 and Multiword DMA modes 0, 1 and 2 and Ultra DMA modes 0, 1, 2, 3, 4, 5 and 6. 133MBps Transfer speed = [(1/30nS) x 2 bytes x 2]. Where 30nS cycle time is 2 clock periods at 15nS each. The ATA-7 standard was released in 2005. With the introduction of Serial ATA, this is the last expected update of the IDE [PATA] bus. SATA is faster, and requires a smaller cable, which means better air flow in the Case.



Serial ATA: (Ver 1.0) High Speed Serialized AT Attachment
Serial version of the IDE [ATA] spec. Uses a 4 conductor cable with two differential pairs [Tx/Rx], plus an additional three grounds pins and a separate power pin. Data runs at 150MBps [1.5GHz] using 8B/10B encoding and 250mV signal swings. Serial ATA is not compatible with the IDE [Parallel ATA] because the connectors are different, the voltage levels are different, and data format is different [SATA sends a bit at a time while PATA sends 16 bits at once]. SATA will not interface with the IDE bus. No cable can be made to connect SATA with IDE. However a converter may be purchased which translates SATA to PATA. One module appears as a 2" x 2" board, for $50 and converts IDE controllers 66/100/133/150 MB/s to Serial ATA 150.

ATA-# interface for disk drives; defines the Physical layer, Electrical layer and Signaling protocol. The speed of data transfer depends on the Transfer mode used. There are 3 main Transfer modes: PIO, Multiword DMA, and Ultra DMA. All transfer rates listed above are best case [Mulit-word/DMA transfers].

PIO Modes: 0 [3.3MB/s], 1 [5.2MB/s], 2 [8.3MB/s], 3 [11.1MB/s], 4 [16.7MB/s]
Multiword DMA Modes: 0 [4.2MB/s], 1 [13.3MB/s], 2 [16.7MB/s]
Ultra DMA Modes: 0 [16.7MB/s], 1 [25.0MB/s], 2 [33.3MB/s], 3 [44.4MB/s], 4 [66.7MB/s], 5 [100.0MB/s]

The hard drive, computer, and software determine the mode used: Programmed Input/Output (PIO), Direct Memory Access (DMA). Addressing on the bus is defined by; CHS (Cylinder, Head, Sector)

Power (+5 / +12volts) is supplied over a four pin connector (unless the 50-pin connector is used). There are a number of power (down) modes defined: Active, Idle, Standby, and Sleep.
Active: normal drive operation.
Idle: the electronics power down but still receives commands.
Standby: the drive spins down and the electronics power down.
Sleep: every thing is powered down, the electronics will not respond except for a power reset.

The early specifications defined the data cable as a normal 40 pin ribbon cable with a 40 pin IDC connector. The latest standard(s) define the same 40 pin connector, but have increased the ribbon to 80 pins - the additional 40 pins being dedicated to ground pins. Data transfers are made at either 8 or 16 bits.
The normal PC cables have three connectors, one for the mother board (at one end) and two for device attachment. One at the opposite end, the other about 6 inches away.

{IDE/ATA Bus Index}


IDE Interface IC Vendors

Data is carried at standard TTL levels over the Parallel ATA [PATA] interface, or IDE interface.
A chart comparing TTL and CMOS threshold levels is provided on the Logic Threshold Voltage Levels page.
The bus is source [series] terminated with a 33 ohm resistor. This page lists Glue Logic TTL devices.

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Cirrus Logic {Disk Controller ICs}

HighPoint Technologies, Inc. {ATA 100/ 133 non-RAID / RAID Disk Controller, RAID 0, 1, 5, 10, JBOD}

Hitachi {ATA-5 compliant memory controller, Mode 4 (66.6 Mbytes/sec)}

Silicon Image Inc {Ultra ATA/100 PCI to ATA Host Controllers}

Silicon Storage Technology, Inc. 'SST' {ATA Flash Disk Controller}

Winbond Electronics Corp. {Power PC I/O Controller-Port Controller-IDE Interface-CDROM Decoder}

Zilog {PCMCIA / Storage Controller ICs}

Another listing of PC Chip Set Manufacturers

All other IC Manufacturers

{ATA/IDE Bus Interface Index}

Ultra ATA doubles the data transfer rate (over Fast ATA) by using the both edges of the strobe

Ultra-ATA/Fast-ATA Strobe, Transfer Timing, and Fast ATA Read Transfers
Ultra ATA Timing

ATA Online Standards Info

Technical Committee T13; AT Attachment: www.t13.org

{Hit the link above to down load the current draft specifications from each working group. Keep in mind that only work on version 7 and 8 are active.
Also that these specification come in multiple volumes, and only the Physical portion is listed below. The rev level indicated may not be the latest.}

ATA-1; AT Attachment Interface (ATA-1); American National Standard X3.221-1994
ATA-2; AT Attachment Interface with Extensions (ATA-2) (ANSI X3T10/948D Rev. 3)
ATA-3; AT Attachment Interface (ATA-3) (ANSI X3T10/2008D Rev. 7b)
ATAPI; AT Attachment with Packet Interface (ATAPI) (X3T10/1120D Rev. 2)
ATA/ATAPI-4; AT Attachment with Packet Interface Extension (ATA/ATAPI-4) (T13/1153D Rev. 18)
ATA/ATAPI-5; AT Attachment with Packet Interface Extension (ATA/ATAPI-5) (T13/1321D Rev. 3)
ATA/ATAPI-6; AT Attachment with Packet Interface Extension (ATA/ATAPI-6) (T13/1410D Rev. 3b)
ATA/ATAPI-7; AT Attachment with Packet Interface Extension (ATA/ATAPI-7) (T13/1532D Vol 1 Rev. 2)
ATA/ATAPI-7; AT Attachment with Packet Interface Extension (ATA/ATAPI-7) (T13/1532D Vol 2 Rev. 2)
ATA/ATAPI-7; AT Attachment with Packet Interface Extension (ATA/ATAPI-7) (T13/1532D Vol 3 Rev. 2)
AT Attachment - 8 ATA/ATAPI; Parallel Transport (ATA8/APT)
ATA/ATAPI-8; AT Attachment Serial Transport / Parallel Transport & Command Set (ATA/ATAPI-8)
Currently the latest released version is revision 7. ATA/ATAPI-8 has not yet been released, and as noted seen with two different titles.
I don't expect any additional IDE Specifications to be released, after the ATA-8 IDE Specification

Serial ATA: (Ver 1.0) High Speed Serialized AT Attachment
Serial version of the IDE [ATA] spec. Uses a 4 conductor cable with two differential pairs [Tx/Rx].
Data runs at 150MBps [1.5GHz] using 8B/10B encoding and 250mV signal swings.

{IDE/ATA Bus Interface Index}


IDE Connectors and Cables

Power (4 pin connector, 0.2 centers), uses an 18 AWG cable;
A separate connector does not exist on all types of interfaces, CardBus for example.
1: +12volt
2: +12v Ground [GND]
3: +5v Ground [GND]
4: +5volt
Data (70 to 90 ohms cable impedance, 30 AWG wire size, IDC termination)
..... (ATA-1 to ATA-4) 40 pin ribbon / IDC connector / flat cable (stranded 28AWG) 18 inches in length [Maximum cable length]
..... (ATA-5 / ATA-6) 80 pin ribbon/IDC cable, 40 pin connector, which will mate with ATA-2/ATA-1, 18 inches in length (12 inches host to device 0, 6in device 0 to 1).

The drive connector is a 40 pin header; with 2 rows of 20, at 0.1 inch spacing. The 40 pin cable requires an additional power cable. The connector is keyed, with pin 20 removed, the mating IDE connector should have the socket of pin 20 blocked, it may be polarized [IDC Definition]. The data and power may be combined into one hybrid connector. Also, there may be a 44 pin header which is used. Placed before pin 1, will be a key, followed by two sets of pins which may be used by the board. The additional pins are not transmitted over the 40 pin cable. An additional 68-pin connector is defined by the standard. The 68-pin connector is the same used by PCMCIA, and allows the device to be compliant with PC Card ATA mode.

Circuit Assembly Corp. {IDE Connectors Disk Drive/Headers}

Foxconn Electronics {IDE Connector}


IDE Parallel Cable, Physical Length
IDE cable drawing
ATA Ribbon Cable





For cables to function properly in ATA applications, the first connector should be the "Blue" connector. If using a two connector assembly, the second connector should be the "Black" connector. If a three connector cable is required all three "Blue, Gray & Black" connectors should be used in the proper order with "Blue" and "Black" on the ends with "Gray" in the middle. The end may be terminated so that they both face in one direction or with one facing up and the other facing down.


40-Pin IDE Connector PinOut
Pin # Signal Function Pin # Signal Function
1 Reset 2 Ground
3 Data 7 4 Data 8
5 Data 6 6 Data 9
7 Data 5 8 Data 10
9 Data 4 10 Data 11
11 Data 3 12 Data 12
13 Data 2 14 Data 13
15 Data 1 16 Data 14
17 Data 0 18 Data 15
19 Ground 20 Key [Void]
21 DMARQ 22 Ground
23 DIOW- 24 Ground
25 DIOR- 26 Ground
27 IORDY 28 CSEL
29 DMARK- 30 Ground
31 INTRQ 32 IOCS16-
33 DA1 34 PDIAG-
35 DA0 36 DA2
37 CS1FX- 38 CS3FX-
39 DASP- 40 Ground

The 40 pin ATA connector pinout and cable pinout is shown above. The 80 pin cable pinout is about the same as above, except that all the signal names listed above are now odd pins in the cable; how ever it's still a 40 pin connector so the table is true for the connector but not the 80 pin cable. The 80-pin cable has all the even cable wires connected to ground. So each pin listed above after pin 1 moves down one or more pin numbers. Pin 2 [Ground] moves to pin 3, Pin 3 has to move to pin 5, Pin 4 has to move to pin 7, pin 5 has to move to pin 9, and so on; using only odd number pins - as all even conductors in the cable are used for ground. At the end of the list pin 40 [ground] is pin 79, while pin 80 is also ground [even pin]. The only exception is pin 34 [PDIAG] which is connected to ground in the cable. Which makes both pin 67 and 68 ground pins in the cable. True for the 80-pin cable, remember the connector remains unchanged, only the cable pin-out changes.

IDE Power Connector Pin-Out
Pin # Signal Function 18 AWG Wire
1 +12V DC Yellow
2 +12V Return Black
3 +5V Return Black
4 +5V DC Red

Recommended wire size is 18AWG. for the power supply interface. The wire color codes were derived from the ATX Motherboard specification.

{ATA Bus Interface Index}


IDE Hard Drive Manufactures

This is a general listing of Personal Computer IDE Hard drive manufacturers.
There is another listing for other bus interface types which may be found on the Computer Hard Drive Manufactures page.
The different types of disk drive bus interface types are listed below. Keep in mind that the Parallel ATA [PATA] Bus is being replaced by the Serial ATA: [SATA] bus.
Internal Interface types; ATA, Ultra ATA, SATA [Desk-top], SCSI, Ultra SCSI, Serial SCSI, SATA [Enterprise]
External Interface types; SATA [Desktop], SCSI, Serial SCSI [Enterprise], Fibre Channel [Enterprise]

Adtron Corporation {Solid State IDE 2.5" UDMA-100, IDE 3.5" UDMA-66, RAID}

Fujitsu {Modile 2.5 inch IDE}

Hitachi {2.5 inch ATA-5 hard disk drive}

HP {160GB Ultra ATA/100}

Samsung {Ultra ATA - 100}

Seagate Disc Storage {Ultra ATA/100}

Toshiba Hard Drives {1.8"; 80GB/120GB/240GB, 100MBps Ultra DMA, Parallel ATA (PATA), 4200rpm}

Western Digital Corp. {SATA 150MBps, SATA 300MBps, EIDE Drive, Enterprise, Desktop, Mobile, External Hard Disk Drives}

{IDE/ATA Bus Interface Index}


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Modified: 2/26/12
Copyright © 1998 - 2012 All rights reserved Leroy Davis