Bios limits
  Original chs limits of dos combined with IDE hardware limits
    c 1024, h 16, s 63 = 504 MiB/528.4 MB (decimal).

  PC Bios limit of 1024 cylinders (int 13).

  Forces OS to be in 1st 1024 cylinders.
    Even if software patch exists, it is loaded after os.

  Fix (Int 13 extension)
    New bios with an extended int 13 code to allow > 1024.

    Requires software to know about it.

  Applies only to ATA (IDE)
    SCSI interfaces included ROM compatible with its chs structure.