PC Hardware Help

IDE (Integrated Drive Electronics) Interface

IDE is an antiquated interface based on the 16-bit Industry Standard Architecture by IBM PC which was used by older storage devices to connect with the motherboard and transfer data. IDE is used with other devices as well, such as CD/DVD drives, zip drives, and tape drives.

ANSI Standards for IDE Drives:

  • IDE/ATA
    First standard for IDE drives. Limited to no more than 528 MB and supports PIO and DMA transfer modes. Speeds range from 2.1 MB per second to 8.3 MB per second.

  • ATA-2/Fast ATA
    Allows for drives larger than 528 MB and up to four IDE devices. Supports PIO and DMA transfer modes. Speeds up to 16.6 MB per second.

  • ATA-3
    Improved version of ATA-2 with about the same performance.

  • Ultra ATA/Fast ATA-2/Ultra DMA/DMA 33
    Improved DMA mode transfer rates with performance up to 33.3 MB per second.

  • Ultra ATA 66/Ultra DMA 66
    Uses 80 wire IDE cable with extra grounding to improve signal strength. Speeds up to 66.6 MB per second.

  • Ultra ATA 100
    Speeds up to 100 MB per second.

  • Ultra ATA 133
    Speeds up to 133MB per second.

  • SATA (Serial ATA)
    Speeds up to 600MB per second (with revision 3.0). Uses smaller cable than PATA IDE drives that only allows for one device per cable.

Transfer Modes

A hard drive can use one of two transfer modes. They are DMA and PIO. DMA transfers data from the hard drive to memory without involving the CPU. PIO mode includes the CPU in the process which makes it slower than DMA.

IDE Cables

Current IDE hard drives use two types of cabling. They are PATA (Parallel ATA) and SATA (Serial ATA).

PATA

A PATA cable is an 80 wire IDE cable used by ATA/66 and higher hard drives. Forty of the wires in a PATA cable are ground wires used to reduce crosstalk. These ground wires alternate in between the signal wires. These cables are also known as ATA/100 cables or Ultra DMA 100/66 cables. Standards before ATA 66 used a regular 40 wire. The only difference between the 80 wire and 40 are the ground wires. They look the same, other than one having twice as many wires, and an 80 wire cable can be used in place of a 40 wire IDE cable. The maximum lengh of a PATA cable is 18 inches.

SATA

A SATA cable is much thinner than a parallel IDE cable and has few wires (minimum of 4). The maximum lengh of a PATA cable is 1 meter. SATA hard drives are faster and are currently on their way to replacing PATA drives. SATA is designed for larger drives with higher performance than PATA hard drives.

EIDE Hard Drive Configurations

Most motherboards by defualt can support up to four IDE devices in a single PC. The motherboard offers a primary and secondary IDE channel. Each channel can support one IDE cable with two devices running off the same cable. One of the devices is configured to act as the master and the other as the slave. These configuartions are configured using either jumpers or DIP switches.

  • Primary channel, master device
  • Primary channel, slave device
  • Secondary channel, master device
  • Secondary channel, slave device

Motherboard manufactures are now transitioning to SATA. It is common for modern motherboards to have as many as eight SATA ports while only supplying one PATA IDE channel. Some are beginning to drop PATA completely.