Computer Hardware
Information about Computer Hard Disk Interfaces

Quick links Interface ABCs ATA ATA-2 ATA-3 ATA-4 ATA-5 ATA-6 ATAPI IDE EIDE Fast ATA Fast IDE RAID SATA SCSI Serial ATA Ultra ATA Hard disk drive definitions SCSI vs. IDE Troubleshooting INTERFACE ABCs A computer interfaces is what allows a computer to send and retrieve information for storage devices such as computer hard disk drives and CD-ROM drives. This section of Computer Hope briefly describes each of the major types of computer interfaces that are used today and that have been used in the past. In addition to a brief explanation, this page also contains technical specifications about each of the interfaces. SCSI VS. IDE The SCSI vs. IDE or EIDE debate is a topic commonly debated between computer users. Below we have created a list of advantages when comparing the two standards to help users decide what standard is best for them. IDE / EIDE Overall, SCSI is a more expensive solution when compared to IDE or EIDE. IDE is commonly a much easier product to setup than SCSI. If a user does not have SCSI ports, requires additional card and additional resources to be taken. SCSI SCSI has greater expandability when compared to IDE and EIDE. SCSI is capable of supporting up to 7 or 15 devices. IDE / EIDE allows 2 two devices per channel. Most computers have 2 channels. The latest SCSI solution is a slightly faster solution when compared to IDE and EIDE. SCSI tends to have more available products for the interface. Larger capacity drives are sometimes released for SCSI before IDE.

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ATA, EIDE, AND IDE INFORMATION

Today, the ATA interfaces are the most commonly used interface on IBM compatible computers to connect to computer hard disk drives, CD-ROM drives, and other types of disk drives. Each of the below standards are compatible with each other, which means a new ATA drive can be used in a computer using an older ATA specification. Finally, when a new feature was introduced in an ATA standard, that feature is also found in future releases. In other words, a ATA-4 is going to have support for PIO modes 0, 1, 2, 3, and 4, even though these were introduced in ATA-1 and ATA-2.

Below is a listing of each of the ATA, IDE, and EIDE standards to help give user a better understanding of the history behind this interface as well as an understanding of each interface's capabilities.

ATA / ATA-1 / IDE

ATA is short for AT Attachment interface and also more commonly known as IDE or ATA-1. ATA was approved as a standard on May 12, 1994 under the ANSI document number X3.221-1994. ATA was first developed by Control Data Corporation, Western Digital, and Compaq. ATA-1 utilizes a 8-bit or 16-bit interface, has a transfer rates of up to 8.3MBps, and has support for PIO modes 0, 1, and 2. Today, ATA / ATA-1 is now considered obsolete.

ATA-2 / EIDE / Fast ATA / Fast IDE / Ultra ATA

ATA-2, more commonly known as EIDE, and sometimes known as Fast ATA or Fast IDE, is a standard approved by ANSI in 1996 under document number X3.279-1996. ATA-2 introduces new PIO modes of 3 and 4, has a transfer rate of up to 16.6MBps, DMA modes 1 and 2, LBA support, and supports drives up to 8.4GB. Today, ATA-2 is now considered obsolete.

ATA-3 / EIDE

ATA-3 is a standard approved by ANSI in 1997 under document number X3.298-1997. ATA-3 added additional security features and the new S.M.A.R.T feature.

ATA-4 / ATAPI-4 / ATA/ATAPI-4

ATA-4 is a standard approved by ANSI in 1998 under document NCITS 317-1998. ATA-4 includes the ATAPI packet command feature, introduces UDMA/33, also known as ultra-DMA/33 or ultra-ATA/33, which is capable of supporting data transfer rates of up to 33MBps.

ATA-5 / ATA/ATAPI-5

ATA-5 is a standard approved by ANSI in 2000 under document NCITS 340-2000. ATA-5 adds support for Ultra-DMA/66, which is capable of supporting data transfer rates of up to 66MBps, and has the capability of detecting between 40 or 80-wire cables.

ATA-6 / ATA/ATAPI-6

ATA-6 is a standard approved by ANSI in 2001 under document NCITS 347-2001. ATA-6 added support for Ultra-DMA/100, and had a transfer rate of up to 100MBps.

ATA layout

Each of the above ATA interfaces that are used with the 3.5-inch disk drives have a 40-pin connector and are capable of supporting up to two drives per interface. However, 2.5-inch hard disk drives utilize a 50-pin connector and PCMCIA utilizes a 68-pin connector Below is an illustration of the ATA interface

Related dictionary definitions

For additional information, please see each of the below dictionary definitions for a brief definition as well as related links and terms.

• ATA definition
• IDE definition
• EIDE definition
• Other hard disk drive definitions
• Other CD definitions

ATAPI

Short for AT Attachment Packet Interface, ATAPI is an extension to ATA which allows support for devices such as CD-ROM drives, Tape drives and other computer peripherals and not just hard disk drives. Before the release of ATA-4 or ATA/ATAPI-4, ATAPI was a separate standard from ATA.

Related dictionary definitions

For additional information, please see each of the below dictionary definitions for a brief definition as well as related links and terms.

• ATAPI definition
• Other hard disk drive definitions
• Other CD definitions

SERIAL ATA (SATA)

Short for SerialATA, SATA 1.0 was first released in August 2001 and is a replacement for the Parallel ATA interface used in IBM compatible computers. SerialATA is capable of delivering 1.5 Gbps (150 MBps) of performance to each drive within a disk array, offers backwards compatibility for existing ATA and ATAPI devices, and offers a thin small cable solution as seen in the below picture. This cable helps make a much easier cable routing and offers better airflow in the computer when compared to the earlier ribbon cables used with ATA drives.

Related dictionary definitions

For additional information, please see each of the below dictionary definitions for a brief definition as well as related links and terms.

• SATA definition

TROUBLESHOOTING

Reference Issue / Question HARD DRIVE Additional information including questions and answers on computer hard disk drives. RAID Additional information and help regarding RAID. SCSI Additional information and help regarding SCSI. FORUM If your question is not listed on this page please try our online forum. CH000695 Can I have more than four IDE devices?