TOPIC ------------------------------------------------------------
This article explains why a high-density disk should not be formatted in 400K
or 800K drives.
DISCUSSION -------------------------------------------------------
If a high-density disk is formatted in a normal 800K or 400K drive, it
functions as an 800K or 400K disk; however, when such a disk is used in the
Apple SuperDrive (formerly Apple FDHD), a dialog box appears stating that the
disk was improperly formatted.
SuperDrive disks have a special notch which allows the SuperDrive to recognize
the media as high density (1.4MB). Standard 800K and 400K drives CANNOT detect
the notch, and will format a high-density disk as a regular 800K or 400K disk.
High-density media should NOT be formatted in a 800K or 400K drive.
High-density disks are physically different from double-density disks and
are tested to a different specification. The coating on high-density disks
is thinner and has finer particles. These disks require a less intense
magnetic field from the read/write head to properly align the magnetic
particles within the data cell during a write cycle.
The magnetic field generated by Apple 800K and 400K drives is too strong and
may cause data loss.
Thus, the SuperDrive, in conjunction with the system software, recognizes that
the high-density disk was formatted improperly and gives the user the option
to re-format it or eject it.