IDE vs ATA vs SATA vs SCSI

There are several different kinds of internal hard drives out there. This is a quick guide to identifying hard drive types based on the interface cable they use to connect to the motherboard.

There are three types of interfaces for hard drives: SCSI, IDE/ATA and SATA.

SCSI: small computer system interface. (pronounced 'scuzzy")

SCSI cables can be up to 12 meters. Narrow SCSI has 8 addresses, wide SCSI has 16. With a single SCSI card you can have 15 or more devices whereas you are only allowed to have 4 devices with an IDE system. There are a variety of SCSI connections, such as 25, 50, 68, 68 LVD, 80 SCA, etc. (where the numbers represent the types of connections). If your drive doesn't look like the IDE/ATA or SATA drives shown below, it is probably a SCSI drive. For more information on identifying SCSI hard drives, see http://utils.blinkenlights.nl/scsi/

Above is an IDE (ATA) drive

IDE. IDE stands for Integrated/Intelligent Drive Electronics. It is an ATA (Advanced Technology Attachment) specification (the terms are often used interchangably). IDE can support cable lengths up to 2 feet long. A single IDE ATA channel can support up to two drives, master & slave. IDE can only access one drive per channel at a time.

Note the 40-pin ribbon cable. There are 80-pin IDE drives but the common type in desktop computers is the 40-pin. See the red edge on the right edge of the ribbon cable? That is Pin 1. Many ribbon cables are built so that they will only connect to the hard drive in one way, one pin is missing on the hard drive and the corresponding pin is blocked on the cable. Some cables don't have the blocked pin though, and those type can be put in upside down. They won't work if they are upside down. Examine the hard drive carefully and you will see a tiny number 1 on one side of the series of pins. That is the edge the red stripe on the ribbon cable should line up with.

There are three IDE (ATA) drive capabilities

This is the most common disk interface for hard drives, CD-ROM drives, etc. It is easy to use, but also the most limited. IDE is integrated into your motherboard. It only allows for 4 devices (so if you have two hard drives, a CD drive, and a DVD drive, you have used up your four devices and won't have room to put in another hard drive. There might be room in the computer's case, but there won't be an open cable to connect it to the motherboard). You can buy a SCSI card and a SCSI drive to add another drive in this situation.

Above is an IDE (ATA) drive and a SATA drive.

The ATA drive on the bottom

The Serial ATA (SATA - Advanced Technology Attachment) drive shown on top uses a seven-pin edge connector with a ribbon cable that's 5/16 in. wide. The cables are thinner, longer, and transfer data faster than IDE or SCSI.

These are newer types of drives, they should be faster, require less power and allow for more efficient and reliable array designs. They won't work with older computers.

This is a SATA data cable

This is a SATA power cable

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