IBM 9 Track
Encyclopedia
IBM 7 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 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...
format it replaced, the magnetic tape
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
is ½ inch (12.7 mm) wide, but has 8 data tracks and one parity
Parity bit
A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
track for a total of 9 parallel tracks. Data is stored as 8-bit
8-bit
The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...
characters, spanning the full width of the tape (including the parity bit). Various recording methods are used to place the data on tape, depending on the tape speed and data density, including PE (phase encoding
Manchester code
In telecommunication and data storage, Manchester code is a line code in which the encoding of each data bit has at least one transition and occupies the same time...
), GCR (group code recording
Group Code Recording
In computer science, group code recording refers to several distinct but related encoding methods for magnetic media. The first, used in 6250 cpi magnetic tape, is an error-correcting code combined with a run length limited encoding scheme...
) and NRZI (non-return-to-zero, inverted, sometimes pronounced "nur-zee"). Tapes came in various sizes up to 3600 feet (1,097.3 m) in length.
The standard size of a byte
Byte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
was effectively set at 8 bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s with the S/360 and 9 track tape.
For over 30 years the format dominated offline storage and data transfer, but by the end of the 20th century it was obsolete, and the last manufacturer of tapes ceased production in early 2002, with drive production ending the next year.
Typical operation
A typical 9-track unit consisted of a tape transport—essentially all the mechanics that moved tape from reel to reel past the read/write and erase heads—and supporting control and data read/write electronics. The transport typically consisted of supply motor, take-up motor, hubs for locking the tape reels in place, a capstan motor (though not necessarily a pinch roller, see below), tape head assemblyTape head
A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa.-Principles of operation:...
, miscellaneous rollers which kept the tape in a precise path during operation, and vacuum columns which prevented tape 'snatch'. Data could become corrupted by stretched tape or variations in tape speed, so the transport had to guide the tape through without damaging its edges, move it with minimal wow and flutter
Wow (recording)
Wow is a relatively slow form of flutter which can affect both gramophone records and tape recorders. In the latter, the collective expression wow and flutter is commonly used.-Gramophone records:...
, and give it a tension that was low but sufficient to keep the tape in constant contact with the read/write head.
To load a tape, an operator would remove the protective ring (frequently called a "tape seal belt" because its purpose was to prevent humidity and dust on the media) from the outside of the tape reel and install the tape on the supply hub, then thread the tape leader through the various roller assemblies and onto the take-up reel, installing three or four winds of tape to provide enough friction for the take-up motor to be able to pull the tape. The operator then initiated an automatic sequence, often by a single press of a button, that would start the vacuum system, then move the tape forward until the beginning-of-tape (BOT) foil strip was detected by an optical sensor in the tape path. The control electronics would then indicate to the controlling computer that the unit was ready for operation.
Like its audio counterpart, moving tape past the read/write heads on 9-track digital required precise control, accomplished by a capstan motor. The capstan motor was designed for very smooth operation. Feedback to the control electronics was accomplished by a tachometer, usually an optical "tone wheel", to control tape velocity. Starting and stopping the capstan was controlled by ramp generators to ensure a properly sized inter-record gap, the gap between blocks of information.
The vacuum system provided a physical buffer between the precision movements of the capstan and the large movements of the reels by storing a short length of tape in the vacuum column under relatively low tension. The vacuum columns were chambers open at one end, the openings being in line with the tape path before and after the capstan and roller assemblies. The amount of tape in the column was controlled by four optical or vacuum sensors on the sides of the columns. The control electronics kept the curve of the tape loop between the two inner sensors, cueing the supply reel to feed more or the take-up reel to take more as necessary. The outer two sensors, at the very top and bottom of the columns, served to sense malfunctions in the feed mechanism during operation, prompting the control electronics to shut off all operation of the tape transport and vacuum system to prevent damaging the tape. Because of the tension provided by the vacuum columns and the design of the tape path, tape was usually kept in sufficient contact with the relatively high-friction coating on the capstan that a pinch roller was not used.
Tape motion on many systems was bidirectional, i.e., tape could be read either forward or backward at the request of the controlling computer. Because the supply vacuum column kept a small, constant tension in the reverse direction, the capstan could feed backwards without the tape bunching up or jumping out of path. Unlike most audio tape systems, the capstan and head assemblies were always in contact with the tape, even during fast forward and rewind operations. On some units, manufacturers installed a "fast search" capability which could move the tape quickly a certain number of blocks, then bring the tape to a halt and go back to read the requested data at normal speed.
Tapes included an end-of-tape (EOT) foil strip. When EOT was encountered, the unit would either halt or rewind the tape onto the supply reel, depending on the unit's design. The sensing of BOT and EOT was achieved by shining a small lamp at the tape's surface at an oblique angle. When the foil strip (glued to the tape) moved past the lamp a photo-receptor would see the reflected flash of light and trigger the system to halt tape motion. This is the main reason that photographic flash cameras were not allowed in data centers since they could (and did) trick the tape drives into falsely sensing BOT and EOT.
The above describes a typical transport system; however, manufacturers engineered many alternative designs. For example, some designs used a horizontal transport deck where the operator simply set the tape reel in the supply reel bay, closed the door and pressed the load button, then a vacuum system would draw the tape along the path and onto a take-up hub within the mechanism. Some designs eliminated the vacuum columns in favor of a microprocessor-controlled direct drive design.
Technical details
9-track 800 NRZI and 1600 PE (phase encoding) tapes utilized a .60" inter-record gap (IRG) placed between data records to allow the tape to stop. 6250 GCR tapes used a very tight .3" IRG. 9-track tapes had reflective stickers placed near (10', 14') each end to signal beginning of tape (BOT) and end of tape (EOT) to the hardware. Nine-track tapes commonly had densities of 800, 1600, and 6250 cpi, giving approximately 20MB, 40MB and 140MB respectively on a standard 2400' tape. Signaling EOT (end of tape) with space remaining to write trailer blocks allowed support for multivolume labelled tapes.IBM generations
| IBM Model | 2400 Series | 3400 Series |
|---|---|---|
| Model numbers | 2401, 2415, 2420, 2440 | 3410, 3420, 3422, 3440 |
| Density (bits/in/track) | 800, 1600 | 1600, 6250 |
| Tape speed (in/s) | 18.75 - 200 | 120 - 200 |
| Transfer rate (B/s) | 15,000 - 320,000 | 1,250,000 |
| Interblock gap (in) | 0.6 | 0.3 |
| Rewind speed (in/s, avg.) | ||
| Start time (ms) | ||
| Stop time (ms) | ||
| Length of reel (ft) | 2400 max | 2400 max |
| Base composition | Plastic | Plastic |
2400 Series
The 2400 Series Magnetic Tape Units were introduced with the System/360 and were the first to use 9 track tape. The dimensions of the tape and reels were identical to those used with 7 trackIBM 7 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 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...
units, such as the IBM 729
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...
. But older 7 track tapes could only be read and written on special 2400 drives equipped with 7 track read and write heads and the 7 track compatibility option.
3400 Series
The 3400 Series Magnetic Tape Units were introduced with the IBM System/370. The primary advantages of the 3400 system were the higher data density (6250 BPI) and the introduction of the "autoloader" cartridge. Prior to the autoloader cartridge, tapes were sealed in a plastic "tape seal belt" that surrounded the reel and provided contamination protection and rack-hanging capability. The 3420's autoloader cartridge enabled the tape operator to mount the reel directly on the hub without having to remove the seal belt. This provided a significant time savings since the operator did not have to remove/replace the belt or thread the tape onto the take-up reel.The maximum data capacity of a 2400 ft reel, blocked at 32,767 bytes and recorded at 6250 BPI was 170 megabytes. Typically, much smaller block sizes, such as 4K (4,096 bytes) were used, in which case the storage capacity of the tape was reduced by 33%, to 113 megabytes.
Standards
- ANSIAnsiAnsi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....
INCITSINCITSThe InterNational Committee for Information Technology Standards, or INCITS , is an ANSI-accredited forum of IT developers. It was formerly known as the X3 and NCITS....
40-1993 (R2003) Unrecorded Magnetic Tape for Information Interchange (9-Track, 800 CPI, NRZI; 1600 CPI, PEManchester codeIn telecommunication and data storage, Manchester code is a line code in which the encoding of each data bit has at least one transition and occupies the same time...
; and 6250 CPI, GCRGroup Code RecordingIn computer science, group code recording refers to several distinct but related encoding methods for magnetic media. The first, used in 6250 cpi magnetic tape, is an error-correcting code combined with a run length limited encoding scheme...
) - ISO/IEC 1863:1990 9-track, 12.7 mm (½ in) wide magnetic tape for information interchange using NRZ1 at 32 ftpmm (800 ftpi) - 32 cpmm (800 cpi)
- ISO/IEC 3788:1990 9-track, 12.7 mm (½ in) wide magnetic tape for information interchange using phase encoding at 126 ftpmm (3 200 ftpi), 63 cpmm (1600 cpi)
- ANSI INCITS 54-1986 (R2002) Recorded Magnetic Tape for Information Interchange (6250 CPI, Group Coded Recording)
- ANSI INCITS 27-1987 (R2003) Magnetic Tape Labels and File Structure for Information Interchange
Other drive manufacturers
- AmpexAmpexAmpex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...
- AnritsuAnritsuis a Japanese corporation that is in the test and measurement market. Products include microwave, RF, and optical signal generators , spectrum analyzers, and network analyzers. It was formed with the merger of two companies, the Annaka Corporation and Kyoritsu Electric in Japan in 1931. In 1990...
- BurroughsBurroughsThe Burroughs Corporation was a major American manufacturer of business equipment. The company was founded in 1886 as the American Arithmometer Company and was assimilated in the 1986 merger that resulted in the creation of Unisys. The company's history paralleled many of the major developments in...
- Cipher Data Products
- Control Data
- Digi-Data
- FujitsuFujitsuis a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. It is the world's third-largest IT services provider measured by revenues....
- Hewlett-PackardHewlett-PackardHewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
(incl. Dynec/Dymec) - Kennedy
- Innovative Data Technology (IDT/Alston)
- Laser Magnetic Storage / PhilipsPhilipsKoninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
LMS / Plasmon LMS - M4 Data
- Overland Data
- PerkinElmerPerkinElmerPerkinElmer, Inc. is an American multinational technology corporation, focused in the business areas of human and environmental health, including environmental analysis, food and consumer product safety, medical imaging, drug discovery, diagnostics, biotechnology, industrial applications, and life...
- Pertec ComputerPertec ComputerPertec Computer Corporation , formerly Peripheral Equipment Corporation , was a computer company based in Chatsworth, California which originally designed and manufactured peripherals such as floppy drives, tape drives, instrumentation control and other hardware for computers.Pertec's most...
- QualstarQualstarQualstar Corporation is an American manufacturer of magnetic tape data storage products, based in Simi Valley, California. It was founded in 1984 as a 9 track tape drive manufacturer, and now makes tape library products...
- STCSTC- Education :* S. Thomas' College, Mt Lavinia, a private school in Sri Lanka* South Texas College* South Thames College* Sha Tin College, Hong Kong* Saint Theresa's College, Philippines- Organizations :* Scarborough Town Centre* Space Transport Corporation...
/ Storage Technology Corp, (then: StorageTek (STK) after name change), (acquired by SUN, now a division of Oracle Corp). - Wangco
Media manufacturers
- 3M3M3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
now ImationImationImation is a US based multi-national technology corporation that designs, manufactures and sells recordable data storage media, consumer electronics products and accessories.The company is a 1996 spin off of 3M and is headquartered in Oakdale, Minnesota...
- The first manufacturer of 9 track tape. - Graham MagneticsGraham MagneticsGraham Magnetics, Inc. was chartered as Datatape, Inc. in 1964. By 1966, it had opened its new magnetic tape factory in Graham, TX and changed its name to Graham Magnetics. Until the 1980s, Graham's primary product was half-inch, open-reel magnetic tape. Graham was the last manufacturer of...
- The last manufacturer to produce new 9-track tape (2001).
External links
- At bitsavers.org
- Cipher documentation
- DEC TS11 TU80 (1600 PE) TA78 TA79 TU81(1600 PE, 6250 GCR)
- Fujitsu M244x Tape Drive CE Manual
- HP 7970 Maintenance Course Handouts: 800 NRZI & 1600 PE drives
- IBM 2400 Series Tape Drives Manual
- Kennedy tape models
- M4Data documentation
- Univac UNISERVOUNISERVOThe UNISERVO tape drive was the primary I/O device on the UNIVAC I computer. Its place in history is assured as it was the first tape drive for a commercially sold computer....
IIIA, IIIC Magnetic Tape Subsystem Technical Bulletins
- HP 7976A 7978A 7980A (88780AB) (1600 PE, 6250 GCR) HP 7974A 1600 PE at hpmuseum.net
- A reliable, autoloading, streaming half-inch tape drive (7980A, 88780AB) HP Journal, June 1988
- IBM 9348-012 (1600, 6250)
- Brochures for M4 Data 9906 1600, (-2 → 3200, -5 → 6250), 9914, 9914V (800, 1600, 3200, 6250)
- Qualstar 3400 Series
- Timeline of OEM drive manufacturers