[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Construction and Operation of the Hard Disk | Hard Disk Logic Board ]

Interface Hardware

While the drive electronics on a modern disk are moved to the disk itself, there is still a controller card or integrated controller on the motherboard, that the disk must talk to. The difference between older drives and newer ones is that older controllers actually ran the internals of the disk itself, while the newer ones just run the data interface between the disk and the rest of the system. Every hard disk's logic contains interface hardware to manage this flow of information between itself and the controller it is talking to.

An integrated IDE/ATA controller chip from a Fujitsu hard
disk logic board. While at one time interface control
functions required many different chips, the advantages
of integration have spurred the development of single-chip
interface solutions, even by third parties (Cirrus Logic
doesn't make hard disks.) In many ways it makes more sense
for Fujitsu to use this chip rather than reinvent the wheel.

The interface hardware itself ranges from relatively simple (slower, older IDE/ATA interfaces) to relatively complex (newer, faster IDE/ATA and SCSI interfaces). In particular, SCSI interface hard disks have considerable "smarts" on them to handle the increased sophistication and the wide variety of commands available on that interface.

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