History of IDEATA and Small Form Factor Committee 4460

The original drives (at least at the "home computer" level) had pretty bare drives, and a separate controller. You had to do a lot of fiddling to get the jumpers right on the controller (so it would match the drive) and you had full access to the drive (so it could be completely formatted and you had to deal with bad sectors).

The path to IDE seems to be this. At one point, "hard cards" came along, which plugged into the bus (usually the ISA bus, but I have a vague memory that they also appeared in some other odd computers), but which had the hard drive mounted right on the board. An integrated hard drive, in essence.

But those were big, and not too flexible, so the things were separated out. The controller became built into the drive, with a very minimal interface (basically buffering and I guess some address decoding) plugged into the ISA bus (or later built into the motherboard), that was mainly there so you could mount the drive at the end of a ribbon cable (which the bus wouldn't like without the buffering).

The hard cards, and the later IDE drives, of course were more integrated. No fussing over getting the controller to match the drive, and from the factory the low level formatted was taken care of (with bad sectors blocked out so the user would never see them). You controlled the drive, rather than controlling the controller that controlled the drive.

The same sort of thing happened with SCSI drives. Originally, they were the same MFM drives that were used with the ISA controllers, but instead of the ISA controller, there'd be an SCSI based controller. (Actually, before there was SCSI, there was SASI, which was a more limited but similar bus.) So you'd need an SCSI interface card in your computer, then the SCSI based controller, then the drive. Eventually, the drive and the SCSI based controller became integrated, leaving drives as you know them today.

Michael