Early hard disk drives

Note: this chapter is in outline format and will be fleshed out later

ST-506

Colloquial designation for all early drives based on the Shugart ST-506 drive.

An early 111 MB ST-506-type drive next to a modern 2.5-inch 6.4 GB IDE hard drive.

Had separate control and data cables.

A later (physically smaller) ST-506-type drive with controller and cables. Notice the second drive connector on the data cable. The second control cable connector is visible below the in-use connector on the controller card.

Early ST-506 drives used an encoding method called modified frequency modulation (MFM). Later drives used an encoding method called run-length limited (RLL). The details and differences won't be discussed here except that RLL drives packed 1.5 times as much data into the same space as MFM drives. The first RLL drives were the same ones manufactured as MFM drives but held 50% more data.

A typical ST-506 controller had a single data cable connected to both drives and control cables. Most controllers also had a floppy disk drive controller.

ST-506-type drives are completely obsolete, usually found in museums and electronic surplus stores.

ESDI

A newer type of ST-506 drive. They are completely obsolete but still functional as doorstops.