Floppy Disk Controller - "3mode" Floppy Drive

"3mode" Floppy Drive

Primarily in Japan there are 3,5" high-density floppy drives that support three modes of disk formats instead of the normal two - 1.44 MB (2 MB unformatted), 1.2 MB (1.6 MB unformatted) and 720 KB (1 MB unformatted). Originally, the high-density mode for 3,5" floppy drives in Japan only supported a capacity of 1.2 MB instead of the 1.44 MB capacity that was used elsewhere. While the more common 1.44 MB format worked at 300 rpms, the 1.2 MB format used 360 rpms instead, thereby closely resembling the 1.2 MB format with 15 sectors / track previously found on 5.25" high-density floppy drives. Later Japanese floppy drives incorporated support for both high-density formats (as well as the single-density format), hence the name 3mode. Some BIOSes have a configuration setting to enable this mode for floppy drives supporting it.