9.3. ESDI hard disks and FreeBSD

Copyright (c) 1995, Wilko Bulte <wilko@yedi.iaf.nl> .
24 September 1995.

ESDI is an acronym that means Enhanced Small Device Interface. It is loosely based on the good old ST506/412 interface originally devised by Seagate Technology, the makers of the first affordable 5.25" winchester disk.

The acronym says Enhanced, and rightly so. In the first place the speed of the interface is higher, 10 or 15 Mbits/second instead of the 5 Mbits/second of ST412 interfaced drives. Secondly some higher level commands are added, making the ESDI interface somewhat 'smarter' to the operating system driver writers. It is by no means as smart as SCSI by the way. ESDI is standardised by ANSI.

Capacities of the drives are boosted by putting more sectors on each track. Typical is 35 sectors per track, high capacity drives I've seen were up to 54 sectors/track.

Although ESDI has been largely obsoleted by IDE and SCSI interfaces, the availability of free or cheap surplus drives makes them ideal for low (or now) budget systems.

9.3.1. Concepts of ESDI

9.3.1.1. Physical connections

9.3.1.2. Device addressing

9.3.1.3. Termination

9.3.2. Using ESDI disks with FreeBSD

9.3.2.1. ESDI speed variants

9.3.2.2. Stay on track

9.3.2.3. Hard or soft sectoring

9.3.2.4. Low level formatting

9.3.2.5. Translations

9.3.2.6. Spare sectoring

9.3.2.7. Bad block handling

9.3.2.8. Kernel configuration

9.3.3. Particulars on ESDI hardware

9.3.3.1. Adaptec 2320 controllers

9.3.3.2. Western Digital WD1007 controllers

9.3.3.3. Ultrastor U14F controllers

9.3.4. Further reading

9.3.5. Thanks to...