A standard IBM Compatible PC is equipped with two IDE Controllers, which are called the Primary Controller (IDE 0) and Secondary Controller (IDE 1) You can connect two devices per controller. In all, a standard PC can hold up to four IDE devices.
IDE Cable:
IDE cable with 40 pins, also known as IDE 33 connector, has three controllers on it.
This is capable of connecting two devices. When there is a need to connect only one device it should be plugged into the connector (usually black in color), found at the end of the cable.
Two connectors are close to each other and the connector on the far end connects the main-board.
