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IDE Hard Drive Installation

Each IDE interface in the computer can support a maximum of two devices attached to that interface. When connecting two drives to a single IDE cable, there are no terminators or is any particular order for connecting the drives. However, when two devices are installed, one must be configured as "master" and the other as "slave". Configuration of IDE drives is done with a jumper located somewhere on the drive. The positions of the jumpers may not be indicated near the jumper pins, although most manufacturers add documentation somewhere on the drive.

When installing a second IDE hard drive in your system, you may have to adjust settings on the existing drive to allow it to work with the new drive. For example, many Western Digital Caviar drives can have a jumper in one of four different positions. These drives typically document jumper positions for Master (MA), Slave (SL), and Cable Select (CS). What they do not always show is a fourth position that the drive ships in, sometimes identified as Single-drive Master. The fourth position could be described as "Master, no slave present", while the position identified as "MA" would be for "Master, slave present". Some early Seagate drives required a second jumper to be added only if a slave is present. If you get the positions of the jumpers wrong, the system will not detect the drive, and may not boot.

IDE hard drives
Three different IDE hard drives, all configured as Master. The center drive is a Western Digital drive configured as a Master (single drive) as shipped. To make it a Master with a second drive attached, the jumper must be moved to a position similar to the bottom drive (also a Western Digital drive).

If the drive does not have the jumper positions identified, read any documentation that may have been included with the drive, or contact the manufacturer for the configuration information. Most manufacturers have documentation available for download, printing or on-line viewing available on their website. This is especially useful when replacing or adding drives to older systems.

Connecting two IDE drives. When adding a second drive, configure one as master (MA) and the other as slave (SL). Attach the IDE cable to both drives and to the system board or IDE interface card. Make sure that the red stripe is towards pin 1 in all cases. If the connector on the cable is keyed, it will only fit one direction. Most drives will have pin one closest to the power connector. Look for one of several identifiers to verify this position. The manufacturer may silk-screen the number "1" next to the appropriate end of the IDE connector. There may be a small triangle shaped mark on the drive connector and on the IDE cable connector. More difficult to find, the pin 1 solder pad on the circuit board where the IDE connector attaches, may be square in shape, while the others are round.

Hard drives with ribbons
Configure one drive as master, and the other as slave. In this image, the WD drive on the bottom is configured as Master, while the top drive has its jumper in the slave position.

Other Issues:
Incompatibility between drives: If the system hangs, or fails to detect both hard drives at startup, try reversing the master and slave configurations. Some brands of drive may not be compatible with others, or may only work in one configuration.

UDMA support: Most current drives support UDMA 66 for high-speed data transfer. To take advantage of UDMA 66 support, your system must support the transfer mode, you must use a special 80-wire IDE cable, and both drives on the cable should support the high-speed mode. If any of these conditions are not met, the system may generate a warning, or drop the transfer speed to a lower rate.

Hard drive ribbons
UDMA 66 cables have 80 wires and usually have a blue 40-pin connector on one end. The extra wires are grounded to help minimize interference.

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