Brief history of HDD controllers

The earliest version of IDE controller was bolted directly with hard disk and plugged into a slot as a single unit. This version of IDE is called XT-IDE.

Another successful interface was ST-506/412, developed by Seagate Technology in 1978. The ST-506 interface was first used to connect ST-506 drive (it had capacity around 5MB!).

ESDI interface was used between 1986 and 1991. It was developed by Maxtor Corporation. Because it was very successful, it was later published as an ANSI standard. It is not used today.

SCSI (Small Computer System Interface) is a general-purpose interface used for connecting many devices to the PC (including hard drives, CD-ROMs, tapes). It was standardized in 1986 and is used also widely today.

And last common interface is AT-IDE. This interface is very successful successor to the XT-IDE and is used in the most modern PCs.