Although it may be inside the system case, an HDD is a peripheral device to the motherboard and CPU. An HDD and a computer communicate, that is, pass data to each other, through a drive interface. A drive interface is the bus structure that the device driver, the hard disk device, RAM, and controllers use to pass data requests and the data requested.
HDD interfaces are either word-serial or bit-serial. Word-oriented interfaces transfer data in 8-bit, 16-bit, or 32-bit words using parallel bit signaling. Examples of word-oriented interfaces are the Small Computer Serial Interface (SCSI) and the Parallel Advanced Technology Attachment (PATA). Bit-oriented interfaces interconnect through a host bus adapter (HBA). Examples of bit-oriented interfaces are fibre channel (FC), serial ATA (SATA), and serial attached SCSI (SAS).
The HDD drive interfaces you should know...
