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{{Short description|Magnetic tape format introduced by IBM in 1952}}
[[Image:IBM_704_mainframe.gif|right|thumb|280px|An [[IBM 704]] [[Mainframe computer|mainframe]] with [[IBM 727]] seven-track tape drives on the left. (image courtesy of [[Lawrence Livermore National Laboratory|LLNL]])]]
[[Image:IBM_704_mainframe.gif|right|thumb|280px|An [[IBM 704]] [[Mainframe computer|mainframe]] with [[IBM 727]] 7-track tape drives on the left]]
[[Image:Tapesticker.jpg|thumb|Reel of 1/2" tape showing beginning-of-tape reflective marker.]]
[[Image:Tapeprotection.jpg|thumb|A [[write protection]] ring had to be inserted in the back of a reel to allow its tape to be written on.]]
[[Image:Tapesticker.jpg|thumb|Reel of 1/2" tape showing beginning-of-tape reflective marker]]
[[Image:Tapeprotection.jpg|thumb|A [[write-protection]] ring had to be inserted in the back of a reel to allow its tape to be written on.]]
[[File:IBM 729 restored.jpg|thumb|upright|A reel of half-inch magnetic tape being loaded onto an [[IBM 729]] tape drive that is attached to an [[IBM 1401]] being restored at the [[Computer History Museum]].]]
[[File:IBM 729 restored.jpg|thumb|upright|A reel of half-inch magnetic tape being loaded onto an [[IBM 729]] tape drive that is attached to an [[IBM 1401]] being restored at the [[Computer History Museum]].]]


[[IBM]]'s first [[magnetic tape data storage]] devices, introduced in 1952, use what is now generally known as '''7 track''' tape. The [[magnetic tape]] 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.
[[IBM]]'s first [[magnetic-tape data storage]] devices, introduced in 1952, use what is now generally known as '''7-track''' tape. The [[magnetic tape]] is {{convert|1/2|in|mm}} 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 column (tape drive)|vacuum column]]s 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.
These tape drives were mechanically sophisticated floor-standing drives that used [[Vacuum column (tape drive)|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==
==Technical details==
; Density : Initial recording density was 100 characters per inch. Later models supported 200, 556 and 800 characters per inch.
; 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.
; 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 1.5ms delay for the stopped tape to reach its full reading or writing speed.
; 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.
; 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]] : A removable plastic ring in the back of the tape reel was inserted to indicate writing should be permitted.
; [[Write protection]] : A removable plastic ring in the back of the tape reel was inserted to indicate that writing should be permitted.


==Generations==
==Generations==
{| class="wikitable" style=" margin-left: 1em;"
{| class="wikitable"
!rowspan="2"|
! IBM Model
!colspan="5"| IBM model
|-
! 726
! 726
! 727
! 727
Line 24: Line 27:
! 7330
! 7330
|-
|-
| Density (chars/in)
! Density (chars/in)
| 100
| 100
| 200
| 200
Line 31: Line 34:
| 200, 556
| 200, 556
|-
|-
| Tape speed (in/s)
! Tape speed (in/s)
| 75
| 75
| 75
| 75
Line 38: Line 41:
| 36
| 36
|-
|-
| Transfer rate (chars/s)
! Transfer rate (chars/s)
| 7,500
| 7,500
| 15,000
| 15,000
Line 45: Line 48:
| 7,200 20,016
| 7,200 20,016
|-
|-
| end of record gap
! End-of-record gap
| 1 Inch <br> 100 chars <br> 16.67 words
| 1 inch <br> 100 chars <br> 16.67 words
| 0.75 Inches <br> 150 chars <br> 25 words
| 0.75 inches <br> 150 chars <br> 25 words
| 0.75 Inches <br> 186 chars <br> 31 words
| 0.75 inches <br> 186 chars <br> 31 words
| 0.75 Inches <br> 150, 417, 600 chars <br> 25, 69.5, 100 words
| 0.75 inches <br> 150, 417, 600 chars <br> 25, 69.5, 100 words
| 0.75 Inches <br> 150, 417 chars
| 0.75 inches <br> 150, 417 chars
|-
|-
| Rewind speed (in/s, avg.)
! Rewind speed (in/s, avg.)
| 75, read backwards
| 75, read backwards
| 500
| 500
Line 59: Line 62:
|
|
|-
|-
| Start time (ms)
! Start time (ms)
| 10
| 10
| 5
| 5
Line 66: Line 69:
|
|
|-
|-
| Stop time (ms)
! Stop time (ms)
| 10
| 10
| 5
| 5
Line 73: Line 76:
|
|
|-
|-
| Max. length of reel (ft)
! Max. length of reel (ft)
| 1,400
| 1,400
| 2,400
| 2,400
Line 80: Line 83:
| 2,400
| 2,400
|-
|-
| Base Composition
! Base composition
| cellulose acetate
| cellulose acetate
| [[PET film (biaxially oriented)|PET film]] or <br> cellulose acetate
| [[PET film (biaxially oriented)|PET film]] or <br> cellulose acetate
Line 88: Line 91:
|-
|-
|}
|}
{{Clear}}


===IBM 726===
===IBM 726===
The [[IBM 726]] dual magnetic tape reader/recorder for the [[IBM 701]] was announced on May 21, 1952.
The [[IBM 726]] dual magnetic tape reader/recorder for the [[IBM&nbsp;701]] was announced on May 21, 1952.


===IBM 727===
===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 [[vacuum tube]] era computer systems. It was withdrawn on May 12, 1971.
The [[IBM 727]] Magnetic Tape Unit was announced for the [[IBM&nbsp;701]] and [[IBM&nbsp;702]] on September&nbsp;25, 1953. It became IBM's standard tape drive for their [[vacuum tube]] era computer systems. It was withdrawn on May&nbsp;12, 1971.


===IBM 728===
===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.
The [[IBM 728]] magnetic tape drive was used on the SAGE [[AN/FSQ-7]] computer. It was physically similar to the [[IBM&nbsp;727]], but with significantly different specifications.
* tracks: 6 Data, 1 synchronization
* tracks: 6 data, 1 synchronization,
* words: 6 chars (32 data bits, 1 parity bit, 3 end of file bits)
* words: 6 chars (32 data bits, 1 parity bit, 3 end-of-file bits),
* words/inch: 41.33
* words/inch: 41.33.


===IBM 729===
===IBM 729===
Line 110: Line 112:
===IBM 2400 Series===
===IBM 2400 Series===
The 2400 Series Magnetic Tape Units were introduced with the [[IBM System/360|System/360]]. 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.
The 2400 Series Magnetic Tape Units were introduced with the [[IBM System/360|System/360]]. 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]] and [[IBM 3592|3592]] formats.


==Sources==
==Sources==
Line 116: Line 121:
* [http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)
* [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
**A22-6589-1_magTapeReference_Jun62.pdf – Reference manual for 7 track drives
* [http://www.thegalleryofoldiron.com/OLDTAPELARGE.JPG IBM 727 Magnetic tape unit] (photo) Sold with 705 in 1955.
* [https://web.archive.org/web/20060818220613/http://www.thegalleryofoldiron.com/OLDTAPELARGE.JPG IBM 727 Magnetic tape unit] (photo) Sold with 705 in 1955.


{{commons category}}
{{Magnetic tape data formats}}
{{Magnetic tape data formats}}


{{DEFAULTSORT:Ibm 7 Track}}
{{DEFAULTSORT:Ibm 7 Track}}
⚫
[[Category:Computer storage tape media]]
[[Category:Computer-related introductions in 1952]]
[[Category:IBM storage devices|Tape 7 Track]]
[[Category:IBM storage devices|Tape 7 Track]]
[[Category:History of computing hardware]]
[[Category:IBM 700/7000 series|Tape format]]
[[Category:IBM 700/7000 series|Tape format]]
[[Category:Tape-based computer storage]]
[[Category:Magnetic data storage]]
⚫
[[Category:Computer-related introductions in 1952]]

Latest revision as of 12:10, 29 July 2023

An IBM 704 mainframe with IBM 727 7-track tape drives on the left
Reel of 1/2" tape showing beginning-of-tape reflective marker
A write-protection ring had to be inserted in the back of a reel to allow its tape to be written on.
A reel of half-inch magnetic tape being loaded onto an IBM 729 tape drive that is attached to an IBM 1401 being restored at the Computer History Museum.

IBM's first magnetic-tape data storage devices, introduced in 1952, use what is now generally known as 7-track tape. The magnetic tape is 1⁄2 inch (13 mm) 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

[edit]
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
A removable plastic ring in the back of the tape reel was inserted to indicate that writing should be permitted.

Generations

[edit]
IBM model
726 727 728 729 7330
Density (chars/in) 100 200 248 200, 556, 800 200, 556
Tape speed (in/s) 75 75 75 75
(112.5) 		36
Transfer rate (chars/s) 7,500 15,000 18,750 15,000 41,700 60,000
(22,500 62,500 90,000) 		7,200 20,016
End-of-record gap 1 inch
100 chars
16.67 words 		0.75 inches
150 chars
25 words 		0.75 inches
186 chars
31 words 		0.75 inches
150, 417, 600 chars
25, 69.5, 100 words 		0.75 inches
150, 417 chars
Rewind speed (in/s, avg.) 75, read backwards 500 500
Start time (ms) 10 5 5
Stop time (ms) 10 5 5
Max. length of reel (ft) 1,400 2,400 2,400 2,400 2,400
Base composition cellulose acetate PET film or
cellulose acetate 		PET film or
cellulose acetate 		PET film PET film

IBM 726

[edit]

The IBM 726 dual magnetic tape reader/recorder for the IBM 701 was announced on May 21, 1952.

IBM 727

[edit]

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 vacuum tube era computer systems. It was withdrawn on May 12, 1971.

IBM 728

[edit]

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.

  • 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

[edit]

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

[edit]

The IBM 7330 Magnetic Tape Unit was a low cost slower tape system. It was common on 1400 series computers.

IBM 2400 Series

[edit]

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 seven-track read/write heads, allowing them to read and write seven-track tapes.

Legacy

[edit]

As of 2020, IBM still sells magnetic tape cartridge drives using half-inch wide tape in the Linear Tape-Open and 3592 formats.

Sources

[edit]
Wikimedia Commons has media related to Half inch magnetic tapes.
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