Often, the control circuitry is built into the motherboard, eliminating the requirement for a separate Host Adapter. There are 2 types of IDE interfaces...those for the 8-bit XT bus, and those for the 16-bit AT bus . The cable for IDE contains 40 conductors and has no twists. Like an SCSI cable, the IDE cable uses a Dual-row Pin connector for both ends. A single cable may be used to connect two drives, or two cables may be Daisy-Chained. Most IDE Host Adapters will support two hard drives. The first drive should be jumpered as the Master drive, and the second as the Slave drive. Plug-in IDE Host Adapters are often called Paddle-Boards, and may contain a floppy controller, and serial and parallel ports.
Note: Direction is Controller relative Devices (Harddisks)