Recent from talks
9-track tape
Knowledge base stats:
Talk channels stats:
Members stats:
9-track tape
9-track tape is a format for magnetic-tape data storage, introduced with the IBM System/360 in 1964. The 1⁄2 inch (12.7 mm) wide magnetic tape media and reels have the same size as the earlier IBM 7-track format it replaced, but the new format has eight data tracks and one parity track for a total of nine parallel tracks. Data is stored as 8-bit characters, spanning the full width of the tape (including the parity bit). Various recording methods have been employed during its lifetime as tape speed and data density increased, including PE (phase encoding), GCR (group-coded recording), and NRZI (non-return-to-zero, inverted, sometimes pronounced "nur-zee"). Tapes come in various sizes up to 3,600 feet (1,100 m) in length.
The standard size of a byte was effectively set at eight bits with the S/360 and nine-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.
A typical 9-track unit consists of a tape transport—essentially all the mechanics that moves tape from reel to reel past the read/write and erase heads—and supporting control and data read/write electronics. The transport typically consists of a supply motor, a take-up motor, hubs for locking the tape reels in place, a capstan motor (though not necessarily a pinch roller, see below), tape head assembly, miscellaneous rollers which keep the tape in a precise path during operation, and vacuum columns which prevent tape 'snatch'. Data can become corrupted by stretched tape or variations in tape speed, so the transport has to guide the tape through without damaging its edges, move it with minimal wow and flutter, and give it a tension that is low but sufficient to keep the tape in constant contact with the read/write head.
To load a tape, an operator removes the protective cover (frequently called a "tape seal belt" because its purpose is to prevent humidity and dust on the media) from the outside of the tape reel and installs the tape on the supply hub, then threads 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 initiates an automatic sequence, often by a single press of a button, that closes the protective window, starts the vacuum system, then moves the tape forward until the beginning-of-tape (BOT) foil strip is detected by an optical sensor in the tape path. The control electronics then indicate to the controlling computer that the unit is ready for operation.
Like its audio counterpart, moving tape past the read/write heads on a nine-track digital tape drive requires precise control, accomplished by a capstan motor. The capstan motor is designed for very smooth operation. Feedback to the control electronics is accomplished by a tachometer, usually an optical "tone wheel", to control tape velocity. Starting and stopping the capstan is controlled by ramp generators to ensure a properly sized inter-record gap, the gap between blocks of information.
The vacuum system provides 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 are 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 is controlled by four optical or vacuum sensors on the sides of the columns. The control electronics keep the curve of the tape loop between the two inner sensors, cueing the supply reel to feed more or stop, and the take-up reel to take more or stop, as necessary. The outer two sensors, at the very top and bottom of the columns, serve 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 is usually kept in sufficient contact with the relatively high-friction coating on the capstan that a pinch roller is not used.
Tape motion on many systems is bidirectional, i.e. tape can be read either forward or backward at the request of the controlling computer. Because the supply vacuum column keeps a small, constant tension in the reverse direction, the capstan can feed backwards without the tape bunching up or jumping out of its path. Unlike most audio tape systems, the capstan and head assemblies are always in contact with the tape, even during fast forward and reverse operations, only moving the head assembly away from the tape path during high-speed rewind. On some units, manufacturers provided a "fast search" capability which can 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.
Hub AI
9-track tape AI simulator
(@9-track tape_simulator)
9-track tape
9-track tape is a format for magnetic-tape data storage, introduced with the IBM System/360 in 1964. The 1⁄2 inch (12.7 mm) wide magnetic tape media and reels have the same size as the earlier IBM 7-track format it replaced, but the new format has eight data tracks and one parity track for a total of nine parallel tracks. Data is stored as 8-bit characters, spanning the full width of the tape (including the parity bit). Various recording methods have been employed during its lifetime as tape speed and data density increased, including PE (phase encoding), GCR (group-coded recording), and NRZI (non-return-to-zero, inverted, sometimes pronounced "nur-zee"). Tapes come in various sizes up to 3,600 feet (1,100 m) in length.
The standard size of a byte was effectively set at eight bits with the S/360 and nine-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.
A typical 9-track unit consists of a tape transport—essentially all the mechanics that moves tape from reel to reel past the read/write and erase heads—and supporting control and data read/write electronics. The transport typically consists of a supply motor, a take-up motor, hubs for locking the tape reels in place, a capstan motor (though not necessarily a pinch roller, see below), tape head assembly, miscellaneous rollers which keep the tape in a precise path during operation, and vacuum columns which prevent tape 'snatch'. Data can become corrupted by stretched tape or variations in tape speed, so the transport has to guide the tape through without damaging its edges, move it with minimal wow and flutter, and give it a tension that is low but sufficient to keep the tape in constant contact with the read/write head.
To load a tape, an operator removes the protective cover (frequently called a "tape seal belt" because its purpose is to prevent humidity and dust on the media) from the outside of the tape reel and installs the tape on the supply hub, then threads 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 initiates an automatic sequence, often by a single press of a button, that closes the protective window, starts the vacuum system, then moves the tape forward until the beginning-of-tape (BOT) foil strip is detected by an optical sensor in the tape path. The control electronics then indicate to the controlling computer that the unit is ready for operation.
Like its audio counterpart, moving tape past the read/write heads on a nine-track digital tape drive requires precise control, accomplished by a capstan motor. The capstan motor is designed for very smooth operation. Feedback to the control electronics is accomplished by a tachometer, usually an optical "tone wheel", to control tape velocity. Starting and stopping the capstan is controlled by ramp generators to ensure a properly sized inter-record gap, the gap between blocks of information.
The vacuum system provides 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 are 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 is controlled by four optical or vacuum sensors on the sides of the columns. The control electronics keep the curve of the tape loop between the two inner sensors, cueing the supply reel to feed more or stop, and the take-up reel to take more or stop, as necessary. The outer two sensors, at the very top and bottom of the columns, serve 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 is usually kept in sufficient contact with the relatively high-friction coating on the capstan that a pinch roller is not used.
Tape motion on many systems is bidirectional, i.e. tape can be read either forward or backward at the request of the controlling computer. Because the supply vacuum column keeps a small, constant tension in the reverse direction, the capstan can feed backwards without the tape bunching up or jumping out of its path. Unlike most audio tape systems, the capstan and head assemblies are always in contact with the tape, even during fast forward and reverse operations, only moving the head assembly away from the tape path during high-speed rewind. On some units, manufacturers provided a "fast search" capability which can 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.
Recent media