IBM's first
magnetic-tape data storage
Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording.
Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later 9-tr ...
devices, introduced in 1952, use what is now generally known as 7-track tape. The
magnetic tape
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magne ...
is 1/2" wide, and there are six data tracks plus one parity track for a total of seven parallel tracks that span the length of the tape. Data is stored as six-bit characters, with each bit of the character and the additional parity bit stored in a different track.
These tape drives were mechanically sophisticated floor-standing drives that used
vacuum columns to buffer long U-shaped loops of tape. Between active control of powerful reel motors and vacuum control of these U-shaped tape loops, extremely rapid start and stop of the tape at the tape-to-head interface could be achieved. When active, the two tape reels thus fed tape into or pulled tape out of the vacuum columns, intermittently spinning in rapid, unsynchronized bursts resulting in visually striking action. Stock shots of such vacuum-column tape drives in motion were widely used to represent "the computer" in films and television.
Technical details
; Density : Initial recording density was 100 characters per inch. Later models supported 200, 556 and 800 characters per inch.
; Inter-record gap : A gap (initially one inch, later 3/4 inch) between records allowed the mechanism time to start and stop the tape.
; Latency : There was only a 1.5 ms delay for the stopped tape to reach its full reading or writing speed.
; Markers : Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers.
;
Write protection
Write protection is any physical mechanism that prevents writing, modifying, or erasing data on a device. Most commercial software, audio and video on writeable media is write-protected when distributed.
Examples
* IBM -inch magnetic tape r ...
: A removable plastic ring in the back of the tape reel was inserted to indicate that writing should be permitted.
Generations
IBM 726
The
IBM 726
The IBM 726 was IBM's first magnetic tape unit. It was a dual magnetic tape reader/recorder developed for use with the IBM 701 and announced on May 21, 1952. This model of tape unit was shipped with the IBM 701 from December 20, 1952 until Februa ...
dual magnetic tape reader/recorder for the
IBM 701 was announced on May 21, 1952.
IBM 727
The
IBM 727
The IBM 727 Magnetic Tape Unit was announced for the IBM 701 and IBM 702 on September 25, 1953. It became IBM's standard tape drive for their early vacuum-tube era computer systems. Later vacuum-tube machines and first-generation transistor co ...
Magnetic Tape Unit was announced for the
IBM 701 and
IBM 702 on September 25, 1953. It became IBM's standard tape drive for their
vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied.
The type kn ...
era computer systems. It was withdrawn on May 12, 1971.
IBM 728
The
IBM 728
The IBM 728 magnetic tape drive was used on the SAGE AN/FSQ-7 computer. It was physically similar to the IBM 727, but with significantly different specifications.
This is one of several IBM 7 track
IBM's first magnetic-tape data storage d ...
magnetic tape drive was used on the SAGE
AN/FSQ-7
The AN/FSQ-7 Combat Direction Central, referred to as the Q7 for short, was a computerized command and control system for Cold War ground-controlled interception used in the USAF Semi-Automatic Ground Environment (SAGE) air defense network.
The ...
computer. It was physically similar to the
IBM 727
The IBM 727 Magnetic Tape Unit was announced for the IBM 701 and IBM 702 on September 25, 1953. It became IBM's standard tape drive for their early vacuum-tube era computer systems. Later vacuum-tube machines and first-generation transistor co ...
, but with significantly different specifications.
* tracks: 6 data, 1 synchronization,
* words: 6 chars (32 data bits, 1 parity bit, 3 end-of-file bits),
* words/inch: 41.33.
IBM 729
The
IBM 729
The IBM 729 Magnetic Tape Unit was IBM's iconic tape mass storage system from the late 1950s through the mid-1960s. Part of the IBM 7 track family of tape units, it was used on late 700, most 7000 and many 1400 series computers. Like its pred ...
Magnetic Tape Unit was IBM's iconic
tape mass storage system from the late 1950s through the mid-1960s. It was used on
late 700, most 7000 and many
1400
Year 1400 ( MCD) was a leap year starting on Thursday (link will display the full calendar) of the Julian calendar. The year 1400 was not a leap year in the Proleptic Gregorian calendar.
Events
January–December
* Henry IV of England ...
series computers. A new dual gap head assembly allowed read-after-write verification.
IBM 7330
The
IBM 7330
The IBM 7330 Magnetic Tape Unit was IBM's low-cost tape mass storage system through the 1960s. Part of the IBM 7 track family of tape units, it was used mostly on 1400 series computers and the IBM 7040/7044. The 7330 used magnetic tape up to lon ...
Magnetic Tape Unit was a low cost slower tape system. It was common on
1400
Year 1400 ( MCD) was a leap year starting on Thursday (link will display the full calendar) of the Julian calendar. The year 1400 was not a leap year in the Proleptic Gregorian calendar.
Events
January–December
* Henry IV of England ...
series computers.
IBM 2400 Series
The 2400 Series Magnetic Tape Units were introduced with the
System/360
The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applica ...
. Most were
IBM 9 Track format drives, but they could be ordered with seven-track read/write heads, allowing them to read and write seven-track tapes.
Legacy
As of 2020, IBM still sells magnetic tape cartridge drives using half-inch wide tape in the
Linear Tape-Open
Linearity is the property of a mathematical relationship (''function
Function or functionality may refer to:
Computing
* Function key, a type of key on computer keyboards
* Function model, a structured representation of processes in a syste ...
and
3592 formats.
Sources
IBM 726 Magnetic tape reader/recorderBitsavers.org Magnetic Tape Equipment manuals(PDF files)
**A22-6589-1_magTapeReference_Jun62.pdf – Reference manual for 7 track drives
IBM 727 Magnetic tape unit(photo) Sold with 705 in 1955.
{{DEFAULTSORT:Ibm 7 Track
Tape 7 Track
History of computing hardware
Tape format
Tape-based computer storage
Computer-related introductions in 1952