IBM 6580 DisplayWriter floppy disks

The IBM 6580 Displaywriter was a microprocessor based textprocessing system which could also be connected as a terminal to “real” IBM computers. In many ways the Displaywriter was IBM’s first response to CP/M based microcomputers.

This examiner is at best a prototype: No documentation of the floppy layout could be located, so this examiner was written “cold” based on a single floppydisk image.

Some hints if you want to work on this:

I’ll keep the floppy image around, email me if you want a copy.

The character set is (an extended variant of) EBCDIC.

The floppy disk has GA21-9128 label with a single file named “WPE”, and it looks like the filesystem is based on block number in that file.

Record number 1872, which is located at CHS=(37, 0, 1) contains the “superblock”, identified by the string “EHL1” four bytes into the sector.

The superblock is the root in some kind of tree-ish structure, where all records start with a Be16 length and a Octet record type. Some of the records span sectors.