If you take brand new high-density, "preformatted for Macintosh" floppy disks and copy some files off an earlier model Macintosh (such as a Macintosh Plus) to transfer them to a newer model Macintosh (such as a Performa). When you insert the disk in the newer model's drive, you get the message "This disk is unreadable. Do you want to initialize it?"
This happens because you are using high-density disks to perform your file transfer, but the earlier Macintosh and the newer Macintosh do not use the same type of disk drive. The earlier models, along with most original Macintosh II models and some Macintosh SE systems do not have the high-density SuperDrive (or FDHD ð floppy drive, high density) necessary to read and format a high-density disk.
So, if you insert a blank high-density disk in a double-density (800K) drive like the one in a Macintosh Plus, it does not know the difference between a double- density and a high-density floppy, and happily formats your expensive 1.4MB disk as an 800K disk.
When you move this disk to a Macintosh with a SuperDrive, the newer drive recognizes the disk as a high-density floppy by its extra hole. Since the disk has been formatted as 800K instead of as 1.4MB, the SuperDrive misreads it and asks you if you want to initialize it.
+---+------------+---+ +---+------------+---+
| | | @ | High ---->| @ | | @ |
| | | | Density | | | |
| +------------+ | Hole | +------------+ |
| | | |
| +---------+--+ | | +---------+--+ |
| | +-+ | | | | | +-+ | | |
| | | | | | | | | | | | | | | |
| | +-+ | | V | | | +-+ | | V |
+---+---------+--+---+ +---+---------+--+---+
As a temporary workaround, place a small piece of tape over both sides of the extra hole (the one on the upper left when looking at the diskette from the front, as shown in the above diagram) on the high-density disk to trick the Macintosh into treating the disk as a double-density disk. This is a temporary solution, and the tape should be removed and the disk reformatted to the proper size as soon as possible.
Article Change History:
13 Jan 1995 - Added keyword, retitled, and made several technical updates.
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