- IBM 7 track
[
right|thumb|280px|An_IBM_704_mainframe with IBM 727 seven-track tape drives on the left. (image courtesy of LLNL)]IBM 's firstmagnetic tape data storage devices, introduced in 1952, use what is now generally known as 7 track tape. Themagnetic tape is 1/2" wide and there are 6 data tracks plus 1 parity track for a total of 7 parallel tracks that span the length of the tape. Data is stored as 6-bit characters, with each bit of the character and the additional the 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 movies 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 G
Write protection : A removable plastic ring in the back of the tape reel was used to indicate whether writing should be permitted.Generations
IBM 726
The
IBM 726 dual magnetic tape reader/recorder for theIBM 701 was announced on May 21, 1952.IBM 727
The
IBM 727 Magnetic Tape Unit was announced for theIBM 701 andIBM 702 on September 25, 1953. It became IBM's standard tape drive for theirvacuum tube era computer systems. It was withdrawn on May 12, 1971.IBM 728
The
IBM 728 magnetic tape drive was used on the SAGEAN/FSQ-7 computer. It was physically similar to theIBM 727 , 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: 41.33IBM 729
The
IBM 729 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 series computers. A new dual gap head assembly allowed read-after-write verification.IBM 7330
The
IBM 7330 Magnetic Tape Unit was a low cost slower tape system. It was common on 1400 series computers.IBM 2400 Series
The 2400 Series Magnetic Tape Units were introduced with the System/360. Most were
IBM 9 Track format drives, but they could be ordered with 7 track read/write heads, allowing them to read and write 7 track tapes.External links
* [http://www-03.ibm.com/ibm/history/exhibits/701/701_1415bx26.html IBM 726 Magnetic tape reader/recorder]
* [http://www-03.ibm.com/ibm/history/exhibits/701/701_1415bx27.html IBM 727 Magnetic tape unit]
* [http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)
**A22-6589-1_magTapeReference_Jun62.pdf – Reference manual for 7 track drives
* [http://www.thegalleryofoldiron.com/OLDTAPELARGE.jpgIBM 727 Magnetic tape unit] (photo) Sold with 705 in 1955.
_between_records_allowed_the_mechanism_time_to_start_and_stop_the_tape._;_Latency_:_There_was_only_a_1.5ms_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._;_)
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