Quarter inch cartridge tape (abbreviated QIC, commonly pronounced "quick") is a magnetic tape data storage format introduced by 3M in 1972, with derivatives still in use as of 2016. QIC comes in a rugged enclosed package of aluminum and plastic that holds two tape reels driven by a single belt in direct contact with the tape. The tape was originally 1⁄4-inch (6.35 mm) wide and anywhere from 300 to 1,500 feet (91 to 457 m) long. Data is written linearly along the length of the tape in one track (mostly on pre-1980 equipment), or it is serialized and written "serpentine" one track at a time, the drive reversing direction at the end of the tape, each track's data written in the opposite direction to its neighbor. Since the introduction of QIC, it has been widely used and many variations exist. There is a QIC trade association that publishes QIC standards which include interfaces and logical formats. To a very large extent it was the efficiency and openness of this organization which encouraged hardware and software developers to use this type of drive and media.
Features of QIC
The QIC cartridge is distinguished from other types of tape cartridges by the fact that it contains an endless drive belt which is moved at a uniform speed by a motorised capstan. Since the belt is in contact with the tape, this ensures both that the tape moves at uniform speed, and that neutral tension is maintained at all times. This is in contrast to cassette tapes or DATs where the tape is moved past the head by a capstan and pinch wheel, but the takeup reel is driven by a servo motor or slipping clutch.
The tape in a QIC cartridge is not physically attached to the reels and is never completely unwound. This is again different from other cassettes or cartridges, which generally have some form of clip anchoring on at least one end of the tape. To ensure that the tape is never completely unwound, each end has a small beginning or end of tape hole which is detected by an optical sensor, and an "early warning" hole further from each end. If a defective drive—for example with fluff in a sensor—winds the tape past the BOT or EOT marker, the tape will detach from the spool and the cartridge will be unusable unless it is reattached.
The design of the QIC tape cartridge is very robust: the aluminium baseplate is an eighth of an inch thick, and the robust plastic cover can withstand abuse and impacts that would damage other tape formats.
However, because the tape is belt-driven, seeking back and forth can eventually cause the tape to become unevenly tensioned. It is therefore necessary to periodically retension the cartridge. This is accomplished by winding the tape from beginning to end and back in one operation, allowing the belt to equalize itself. For newer QIC drives that use a SCSI interface, there is a SCSI "RETENSION" command to do this.
When the cartridge gets old, the belt may not provide enough friction to turn the takeup spool smoothly. When this happens, the tape will need to be replaced.
In some cases a cartridge must be formatted before use. The capability to do this is in the drive rather than the host computer.
3M Data Cartridge (DC)
The first QIC tape format was the 5.875 in by 3.875 in (150 x 99mm) Data Cartridge (DC) format with two internal belt-driven reels and a metal base. The original product, the DC300, has 300 feet of tape and holds 200 kilobytes. Various QIC DC recording formats have appeared over the years, including:
- QIC-11: a four-track format giving 20 MB on a 450 ft DC300XL cartridge
- QIC-24: nine-track, 45 MB or 60MB on a 450 or 600 ft (DC600A) cartridge respectively 
- QIC-120: 15-track, 125 MB, DC6150 cartridge
- QIC-150: 18-track, 150 MB, DC6150 cartridge
- QIC-525: 26-track, 525 MB on a 1020 ft DC6525 cartridge
- QIC-1350: 30-track, 1.35GB on a DC9135 cartridge
QIC Mini Cartridge (MC)
Later, the smaller Minicartridge (MC) form-factor was introduced. This is 2.375 in by 3.125 in (61 x 80mm) size and is small enough to fit in a 3.5 in drive bay.
|Format||Capacity (MB)||Speed (kB/s)||Tracks|
SLR is Tandberg Data's name for its line of high-capacity QIC data cartridge drives. As of 2005, Tandberg was the only manufacturer of SLR/QIC drives in the world. The largest SLR drive can hold 70 GB of data (140 GB compressed).
QIC Extra, a modification to support longer tapes and thus more data by the Verbatim Corporation, was made possible by making the cartridges physically longer to accommodate larger spools. In many cases a standard QIC drive and backup package can use the extended length to store additional data, however in some cases an attempt to reformat a QIC-EX cartridge fails since the time taken to traverse the extra length triggers a timeout in the drive or controlling software intended to detect a broken tape.
- Larry Coyne (2011). IBM Tape Library Guide for Open Systems. p. 9. ISBN 0738435554.
- Development Standards Adopted by QIC
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