IBM Type 2

IBM Type 2 is a type of 8" floppy disk used by IBM for the 43FD drive used in the 1970s and 1980s on some mainframes and minicomputers such as the 370 and System/34. It uses FM encoding at a track density of 48 tracks per inch and a bit density of 3,408 bits per inch, on double-sided single-density media. There are two subtypes, with different sector layouts and slightly different total storage capacity.

492 KB
This format has an index cylinder of 26 128 byte sectors, and 74 regular data cylinders of 26 sectors of 128 bytes each per side, totalling 3,848 data sectors with a capacity of 492,544 bytes.

568 KB
This format has an index cylinder of 26 128 byte sectors, and 74 regular data cylinders of 15 sectors of 256 bytes each per side, totalling 2,220 data sectors with a capacity of 568,320 bytes.