Floptical

The 21 MB Floptical 3½-inch disk

Floptical refers to a type of floppy disk drive that combines magnetic and optical technologies to store data on media similar to standard 3½-inch floppy disks. The name is a portmanteau of the words "floppy" and "optical". It refers specifically to one brand of drive and disk system, but is also used more generically to refer to any system using similar techniques.

The original Floptical technology was announced in 1988[1][2][3] and introduced late in 1991[citation needed] by Insite Peripherals, a venture funded company set up by Jim Adkisson, one of the key engineers behind the original 5¼-inch floppy disk drive development at Shugart Associates in 1976. The main shareholders were Maxell, Iomega and 3M.

Technical aspects

The technology involves reading and writing data magnetically, while optically aligning the read/write head in the drive using grooves in the disk being sensed by an infrared LED and sensor (a form of visual servo).[4] The magnetic head touches the recording surface, as it does in a normal floppy drive. The optical servo tracks allow for an increase in the tracking precision of the magnetic head, from the usual 135 tracks per inch to 1250 tracks per inch. Floptical disks provide 21 MB of storage. The drive has a second set of read/write heads so that it can read from and write to standard 720 kB and 1.44 MB (1440 KiB) disks as well.[4][5]

To allow for a high degree of compatibility with existing SCSI host adapters, Floptical drives were designed to work as a standard floppy disk drive, and not as a removable hard disk. To ensure this, a "write lockout" feature was added in the firmware. This effectively inhibits writing (including any kind of formatting) of the media. It is possible to unlock the drive by issuing a SCSI Mode Sense Command, 1A 00 20 02 A0. It is unclear how much of a problem this is, and Insite also issued EPROMs where this "feature" was not present.

At least two models were produced, one with a manual lever that mechanically ejected the disc from the drive, and another with a small pinhole into which a paperclip can be inserted, in case the device rejected or ignored SCSI eject commands.

Technical specifications

Unformatted 25 MB
Formatted 20385 kB
Rotational speed 720 rpm[5]
Track density 1250 TPI[5]
Recording density 23980 bpi (RLL)[5]
Transfer from disk 1.6 Mb/s[5]
Buffer transfer rate 2 MB/s[5]
Average seek time 65 ms[5]
Settle time 15 ms[5]
Motor start time 750 ms[5]
Number of heads 2[5]
Cylinders 755[5]
Sectors per track 27
Sector size 256, 512, or 1024 bytes (set at format time)
Interface SCSI
Other Languages
català: Flòptical
español: Floptical
中文: Floptical