80-wire Cables
On an ATA66/100/133 standard 80-wire cable, the Master hard drive or the boot hard drive is placed on the END of the cable. When using Cable Select, the standard 40-wire ATA ribbon cable and the 80-wire cable give different drive behaviors.
The three connectors have typically different colors and attach to specific items:
The blue connector attaches to the motherboard.
The black connector attaches to the primary or master drive.
The gray connector attaches to the secondary or slave drive.
There is a stripe along one side of the cable, which indicates that the wire on that side is attached to Pin 1 of each connector and wire 20 is not connected to anything. Actually, there is no pin in that position. The main purpose of this is to ensure that the cable is attached to the drive in the correct position. Using a cable key was a method through which the manufacturers ensured that the cables were not reversed. Cable key is nothing but a small plastic square that's found on top of the connector on the ribbon cable that clasps onto a notch that's on the connector of the device thus allowing the cable to fix in only one position.
