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.

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Hard Disk Connectors and Cables