Weak sector data

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Some copy protections have what is described as “weak”, “random” or “floated” data.

Each time the “weak” sector is read one or more bytes will change. Their value may be random between consecutive reads of the same sector.

Weak data can only be recorded using modified hardware, so you cannot easily copy these disks.

Only the Extended DSK and UDI 1.1 disk image formats record this type of data.

Copy protection

Weak sectors are used by the Speedlock family of copy protection routines for ZX Spectrum +3 disks.

Usually weak sector data is combined with other techniques for disk copy protection, such as:

  • different sector lengths for different tracks
  • different sector lengths within a track
  • sectors marked as deleted
  • sectors with CRC error
  • incorrect sector header information e.g.:
    • incorrect track number
    • increased sector length

Disk images with weak sectors

Unfortunately, disk images with the weak sector data recorded are rare, so if a program reads the same sector repeatedly then some emulators assume that this sector has weak data. (e.g. Fuse)