The HPA was added with the IDE/ATA-4 specification (see IDE). The device configuration overlay (DCO) lets PC vendors buy drives in a range of sizes from different manufacturers and configure them ...

A 40-wire cable connects the IDE (ATA) CD drive, and an 80-wire cable is used for the IDE (ATA) hard disks. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction requires permission.

Two IDE/PATA drives, on the other hand, could share the same data cable, but only one could use it at a time and thus each required a distinct name. In fact, by the time ATA-2 was approved in 1996 ...