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37-738: Many IBM peripheral devices that are part of System/360, but were adapted from second-generation designs, continued to use SMS circuitry instead of the newer SLT. These included the 240x-series tape drives and controllers, the 2540 card reader/punch and 1403N1 printer , and the 2821 Integrated Control Unit for the 1403 and 2540. A few SMS cards used in System/360 peripheral devices even have SLT-type hybrid ICs mounted on them (see right) . SMS cards are constructed of individual discrete components mounted on single-sided paper-epoxy printed circuit boards . Single-width cards are 2.5 inches wide by 4.5 inches tall by 0.056 inches thick, with

74-497: 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

111-523: A 16-pin gold plated edge connector . Double-width cards are 5.375 inches wide by 4.5 inches tall, with two 16-pin gold plated edge connectors. Contacts are labeled A–R (skipping I and O ) on the first edge connector, and S–Z, 1–8 on the second. The cards are plugged into a card-cage back-plane and edge connector contacts connected to wire wrap pins. All interconnections are made with wire-wrapped connections, except for power bus lines. The back-plane wire-wrap connections were mostly made at

148-417: A capstan shaft in order to create friction necessary to drive the tape along the magnetic heads (erase, write, read). Most magnetic tape recorders use one capstan motor and one pinch roller located after the magnetic heads in the direction of the moving tape. However multiple pinch rollers may also be employed in association with one or more capstans. An example of the application of multiple pinch rollers

185-452: A different configuration in the field he could make additional cuts as needed. This feature was intended to reduce the number of different card types a customer engineer had to carry with him to the customer's site. The card type is a two- to four-letter code embossed on the card (e.g., MX, ALQ ). If the card has a "program cap" the code is split into a two-letter card type code and a two-letter "cap connection" code (e.g., AK ZZ ). When SMS

222-406: A microprocessor-controlled direct drive design. 9-track 800 NRZI and 1600 PE (phase encoding) tapes use a 0.6 inches (15 mm) inter-record gap (IRG) between data records to allow the tape to stop and start between records. 6250 GCR tapes use a tighter 0.3 inches (7.6 mm) IRG. 9-track tapes have reflective stickers placed on the non-data side 10 feet (3.0 m) from the beginning of

259-424: 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

296-434: A time. The disadvantage is that data corruption within a block can cause multiple records to be lost. Capstan (tape recorder) A tape transport is the collection of parts of a magnetic tape player or recorder that move the tape and play or record it. Transport parts include the head, capstan, pinch roller, tape pins, and tape guide. The tape transport as a whole is called the transport mechanism . The tape head

333-480: 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

370-409: A typical transport system; however, manufacturers engineered many alternative designs. For example, some designs use a horizontal transport deck where the operator simply sets the tape reel in the supply reel bay, closes the door and presses the load button, then a vacuum system draws the tape along the path and onto a take-up hub within the mechanism. Some designs eliminate the vacuum columns in favor of

407-405: Is a rotating spindle used to move recording tape through the mechanism of a tape recorder . The tape is threaded between the capstan and one or more rubber-covered wheels, called pinch rollers, which press against the capstan, thus providing friction necessary for the capstan to pull the tape. The capstan is always placed downstream (in the direction of tape motion) from the tape heads. To maintain

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444-444: Is nearly impossible. When this happens a new BOT strip is added to the tape and its former data is considered lost. Nine-track tapes have densities of 800, 1600, and 6250 8-bit bytes per inch, giving approximately 22.5MB, 45MB and 175MB respectively on a tape with the usual length of 2,400 feet (730 m). The 2400 Series Magnetic Tape Units were introduced with the System/360 and were the first to use 9-track tape. The dimensions of

481-408: Is reduced to 113 megabytes. Depending on the operating system, tapes are formatted as either EBCDIC (if IBM equipment is used) or ASCII, and are either "labeled" (if the data is preceded by a tape header, typically containing a tape name and date), "unlabeled" (if the tape contains no header) or have a "non-standard label" (the tape has a header, but it does not conform to the format expected by

518-484: Is the Technics RS-1520 tape recorder, which utilizes two pinch rollers located on opposite sides of a single capstan shaft, providing a more stable transport across two sets of magnetic heads. Dual pinch rollers are also used (along with dual capstans) in auto-reverse cassette decks to drive the tape in both directions as needed. In this case, only one pinch roller is pressed against its corresponding capstan at

555-405: Is the 9348-012 and it is a table top drive, flat mounting, but it autoloads the tape reel and auto threads it. The 9348 supports 1600 and 6250 bpi density tapes. The maximum data capacity of a 2400 ft reel, with 32,767 byte blocks and recorded at 6250 BPI is 170 megabytes. Typically, much smaller block sizes, such as 4K (4,096 bytes) are used, in which case the storage capacity of the tape

592-433: Is the part of a tape recording or playback device which converts the magnetic fluctuations present in the tape into an electrical signal, which is then amplified and sent to speakers or headphones. The tape head is set off-center in a multitrack device in order to record or play one or more tracks running in each direction of the tape (e.g. the two different tracks present on most, if not all, compact cassettes ). The capstan

629-498: The "autoloader" cartridge, first seen in the IBM 2420 model 7. 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 enables the tape operator to mount the reel directly on the hub without having to remove the seal belt. This provides a significant time saving and reduces operator errors, since

666-412: 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

703-432: 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

740-446: The equipment used to read the tape). Data is often written to the tape in blocks, instead of one record at a time. Between blocks, there is an interblock gap, which varies depending on the density, but is typically 5/8 to 3/4 of an inch long. To maximize the amount of data that is stored on a tape, the number of gaps has to be minimized. Additionally, data stored in blocks can be read and written more quickly than data stored one record at

777-424: The factory with automated equipment, but the wire-wrap technology facilitated field-installation of engineering changes by customer engineers. Some card types can be customized via a "program cap" (a double-rail metal jumper bar with 15 connections) that could be cut to change the circuit configuration. Card types with a "program cap" came with it precut for the standard configuration and if a customer engineer needed

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814-543: The operator does not have to remove/replace the belt or thread the tape onto the take-up reel. While the earlier tape drives have vacuum columns, some IBM tape drives such as the 8809 drive (1980's) have a flat mount situation and no vacuum columns exist. Tapes are manually mounted and threaded. The drive supports both 800 and 1600 bpi. This drive is used on the IBM System/36 . On the IBM AS/400 and iSeries there

851-491: 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

888-584: The required tension against the tape heads and other part of the tape transport, a small amount of drag is placed on the supply reel. Tape recorder capstans have a function similar to nautical capstans , which however have no pinch rollers, the line simply being wound around them. The use of a capstan allows the tape to run at a precise and constant speed. Capstans are precision-machined spindles, and polished very smooth: any out-of-roundness or imperfections can cause uneven motion and an audible effect called flutter . The alternative to capstan drive, simply driving

925-478: The requirements of the many different systems in which the cards were used. IBM 2400 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

962-416: 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

999-429: The tape and 14 feet (4.3 m) from the end of the tape to facilitate signaling the hardware to prevent the tape from unwinding from the hubs. These reflective stickers establish the beginning-of-tape (BOT) and end-of-tape (EOT) marks. 10 feet (3.0 m) of leader and trailer tape is sufficiently long to allow the tape to go down and up the air columns and wrap around the hub a few times. The extra 4 feet (1.2 m) in

1036-536: The tape and reels are identical to those used with 7-track units, such as the IBM 729 . But older 7-track tapes can be read and written only on special 2400 drives equipped with 7-track read and write heads and the 7-track compatibility option. The 3400 Series Magnetic Tape Units were introduced with the IBM System/370 . The primary advantages of the 3400 system are the higher data density (6250 BPI) and support of

1073-414: 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

1110-447: 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

1147-425: 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

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1184-472: The tape takeup reel (which was used on some cheap tape recorders), causes problems both with the speed difference between a full and empty reel and with speed variations as described. Dual capstans, where one is on each side of the heads, are claimed to provide even smoother tape travel across the heads and result in less variance in the recorded/playback signal. The pinch roller is a rubberized, free-spinning wheel typically used to press magnetic tape against

1221-401: The tape to a halt and go back to read the requested data at normal speed. Tapes include an end-of-tape (EOT) foil strip. When EOT is encountered while writing, the computer program is notified of the condition. This gives the program a chance to write end-of-tape information on the tape while there is still enough tape to do so. The sensing of BOT and EOT is achieved by shining a small lamp at

1258-402: The tape's surface at an oblique angle. When the foil strip (glued to the tape) moves past the lamp a photo-receptor sees the reflected flash of light and triggers the system to halt tape motion. This is the main reason that photographic flash cameras are not allowed in data centers with 9-track tape drives since they can trick the tape drives into falsely sensing BOT and EOT. The above describes

1295-523: The trailer is to allow the operating system space to write a few blocks of data after the EOT mark to finalize the tape data segment in a multi-volume dataset. Operators commonly clip off a few inches of leader tape when it becomes frayed. If the leading reflective strip becomes detached from the tape it becomes difficult to read the data, since the BOT point of the dataset is no longer easily located and BOT orientation

1332-405: 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 ring (frequently called a "tape seal belt" because its purpose is to prevent humidity and dust on the media) from the outside of

1369-444: Was originally developed, IBM anticipated a set of a couple hundred standard card types would be all that would be needed, making design, manufacture and servicing simpler. Unfortunately that proved far too optimistic as the number of different SMS card types soon grew to well over 2500. Part of the reason for the growth was that multiple digital logic families were implemented (ECL, RTL, DTL, etc.) as well as analog circuits , to meet

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