Early disk controllers were identified by their storage methods and data encoding. They were typically implemented on a separate controller card. Modified frequency modulation (MFM) controllers were the most common type in small computers, used for both floppy disk and hard disk drives. Run length limited (RLL) controllers used data compression to increase storage capacity by about 50%. Priam created a proprietary storage algorithm that could double the disk storage. Shugart Associates Systems Interface (SASI) was a predecessor to SCSI.
Modern disk controllers are integrated into the disk drive. For example, disks called "SCSI disks" have built-in SCSI controllers. In the past, before most SCSI controller functionality was implemented in a single chip, separate SCSI controllers interfaced disks to the SCSI bus.
Sometimes there may be yet another controller between a host adapter and a disk controller - a disk array controller that allows hardware RAID to be formed. Sometimes it may be even physically integrated with an HBA, but it performs different functions.
Patent Application Titled "Magnetic Disk Controller to Process Plural Data Sets for Recording onto a Medium" under Review
Jan 29, 2013; By a News Reporter-Staff News Editor at China Weekly News -- According to news reporting originating from Washington, D.C., by...
Floppy-disk controller conforms to ISA Plug-and-Play standard. (Standard Microsystems' FDC37C667 floppy-disk controller) (Product Announcement)
Nov 10, 1994; Standard Microsystems' FDC37C667 parallel-port Super I/O floppy-disk controller is the first such device to comply with the ISA...