Hard Disk Connectors and Cables

          ┌───O───────────────────────────────────────────┐
          │                Hard Disk Drive                │
          \                                               \
          \                                               \
          │                          Drive Select   Data  │
          │ power  Command Cable        Pins       Cable  │
          └┬────┬─┬┬┬┬┬┬┬┬┬┬┬┬┬─┬┬────┬┬┬┬┬┬┬┬───┬┬┬┬┬┬─┬┬┘
           │oooo│ │││││││││││││ ││          X    ││││││ ││
           \────┘ └┴┴┴┴┴┴┴┴┴┴┴┘▲└┘               └┴┴┴┴┘▲└┘
                               └───────────────────────┴─── Key Slots
      Key
    Slots Cables are keyed with a plug at the position of the key slot, but
          I've seen cables in which the plug has fallen out.

          Attach the cable with pin 1 (which has a colored wire) toward the
          slot.

    power A separate power cable is needed for each drive.  The connector
          is keyed to avoid improper orientation.

  Command This is the wider of the two cables.  It carries control
    Cable information to the drive.  Most systems have two connectors on
          the Command Cable:
          ┌─────────────────┐
          │ Connected to the│
          │ controller      │  (see below)
          └╥─┬─┬─┬─┬─┬─┬─┬─┬┘
colored    ║ │ │ │ │ │ │ │ │   ┌─
   wire═╦═►║ │ │ │ │ │ │ │ │   │On the second hard disk, the Drive Select
   (key ║  ║ │ │ │ │ │ │ │ │   │jumper should be set to the second
   slot ║ ┌╨─┴─┴─┴─┴─┴─┴─┴─┴┐  │position and the terminating resistor
   side)║ │ Connected to the│◄═╡should be removed from the drive.
        ║ │ second hard disk│  └
        ║ └╥─┬─┬─┬─┬─┬─┬─┬─┬┘ ┌
        ║  ║ │ │ │ │ │\t/│ │  │If your cable does not have this twist,
        ╚═►║ │ │ │ │ │ w │ │◄═╡then the first drive must have the
           ║ │ │ │ │ │ i │ │  │Drive Select jumper in the first position.
           ║ │ │ │ │ │ s │ │  └
           ║ │ │ │ │ │/t\│ │   ┌
          ┌╨─┴─┴─┴─┴─┴─┴─┴─┴┐  │If your cable does have the twist, then
          │ Connected to the│◄═╡the Drive Select jumper on the first drive
          │ first hard disk │  │must be in the second position and the
          └─────────────────┘  │terminating resistor should be in place.
                               └

    Drive Hard drives have a double row of pins (usually four or eight
   Select sets) with a jumper across one set.  In most cases, the jumper
          should be across the second set (jumper the first set on the
          first hard disk only if your cable does not have a twist).

          If you can see any printing on the circuit board, you can usually
          figure out which is the side with the first position (DS 0 or
          pin 1, etc.).  Or you can tell the end with pin 1 by looking at
          the back of the controller.  It is the side that has a square
          solder mark.

     Data This is the narrow ribbon cable.  There is one data cable for
    Cable each hard disk.  Attach it with the colored wire toward the
          Key Slot.

█▌Hard Disk Controller Card▐█

             ╔═══ Data Cable for first drive  ╔═ Command Cable ┌─
             ║   ┌────────────────────────────▼───────────────┐│
             ╚══►│ :.::::::             :::::::::::::: ┌────┐ ││
                 │1                    1               └────┘ ││
             ╔══►│ :.::::::         ┌───────┐                 ││
             ║   │1        ┌────┐   │       │  ┌──────┐ ┌────┐││
             ║   │  ┌────┐ └────┘   └───────┘  │      │ └────┘││
             ║   │  └────┘                     └──────┘       ││
             ║   └──────────────────┬┬┬┬┬┬┬┬─┬┬┬┬┬┬┬┬┬┬┬┬┬┬┬┬┬┘│
             ║                      └┴┴┴┴┴┴┘ └┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┘ │
             ╚═ Data Cable for second drive

          Controller cards vary in layout, but the connectors are similar.
          Just take care to connect the Data Cable for each drive to the
          correct connector and make sure that the connector is oriented
          correctly.

          Hard Disk Number: The board usually has HD0 or HD1 printed on it
          to guide you in this momentous decision.

          Connector Orientation: Cables often have a plug to match a
          missing pin, to ensure the proper orientation.

          The side of the cable that has a colored wire is the one to
          connect to pin 1.  To locate pin 1 on the controller, try:

          ■ Look for a 1 printed on the circuit board.  Or...
          ■ If there is a square solder mark on the back side of the
            controller where the pins are connected, this is pin 1. Or...
          ■ Refer to your controller documentation.

See Also: Diskette Drive Cables
          Cables and Pin Outs
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