Recovering Data from Obscure 8 Inch Floppy Disc Formats

The early days of the floppy disc, from its introduction as a read-only means of distributing microcode for IBM System 370 mainframes and peripherals to a ubiquitous part of data entry, word processing, and later personal computing systems, mostly agreed on an eight inch (200 mm) flexible magnetic disc, but varied all over the map in organisation of the data on the disc, with “hard sectored” formats having physical holes marking sector boundaries, “soft sectored” discs relying on sector marks recorded on the medium, number of tracks per inch, sectors per track, sector size, rotation speed, data encoding technique, single or double sided recording, and even direction of rotation. This makes getting data off these vintage media not just a challenge but an adventure. It’s time to hook up the oscilloscope and logic analyser and start digging.

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