Victor 9000 format
A very strange format used by the Sirius One / Victor 9000 computer. This machine ran MS-DOS and CP/M, but had a very unusual disc format:
- Variable speed -- 9-zone Z-CLV. The linear velocity of the disc is held fairly constant by rotating certain blocks of tracks slower than others, and storing more data sectors on the outer ("longer") tracks.
- GCR coding -- specifically, a 4-to-5 GCR code which looks like MFM on a timing histogram.
Other than that, they're pretty standard. A DiscFerret can accurately sample and (in theory) decode these discs.
Low level format
GCR code table
From the source code to CW 0.13 by Karsten Scheibler:
|input (hex)||output (bin)||output (hex)|