Patent GB-753333-A (GB)
Title: Data storage system
IPC: G06F15/10
Filed: 1953-10-22
Abstract: 753,333. Electric digital-data-storage apparatus; electronic counting-apparatus; recording- apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 22, 1953 [Oct. 25, 1952], No. 29188/53. Classes 106 (1) and 106 (4). In a data storage system comprising a magnetic storage device, means for transferring discrete items of data to different addresses on the device during relative movement between the device and the transferring means, and means for selecting a single address, the address selecting means comprises a single address store, and is controlled by means producing an indication of the instantaneous relative positions of the device and transferring means, for selecting a first address and for automatically selecting subsequent addresses without introduction of further addresses into the address store. General arrangement.-The magnetic storage system described is for use with a computer, cared " main machine (not described in detail), and comprises two magnetic drums each divided into two " logical drums." Each of the latter comprises 36 tracks for storing in parallel 36-digit binary numbers, a sync track containing a magnetised spot for marking each of the 2048 digit positions on the storage tracks, and an index track containing a single spot for defining a start position. Before the storage system can operate it must receive three " instructions " from the main machine, viz. : (1) Read Drum or Write Drum Select, which selects the required one of the four logical drums and determines whether data is to be read from or written on the drum; (2) Set Drum, which controls entry of a required first address on the drum from an address register (not shown) into the drum counter 35-45, Fig. 32b; and (3) Copy, which initiates the required read or write operation. If the Copy instruction is repeated, further addresses on the drum will be automatically selected. Fig. 8 illustrates the principle of operation. After the drum 20 passes the start position relative to the readwrite head H, timing pulses obtained from the sync track are applied to the drum counter comprising a series of 11 bi-stable triode trigger circuits, representing powers of 2 as indicated, on which the required address has been previously registered. When the counter produces an " end carry," an output pulse is obtained from a switching circuit S which pulse effects the required read or write operation, the addresses being so located on the drum that the required first address will then be opposite the head H. The timing pulses continue to be applied to the counter, and the circuit S is now arranged to be responsive to " middle carries," produced from the output of the first 7 triggers once for every 128 input pulses, whereby further consecutively numbered addresses, spaced 128 positions apart, are made available. Also, since those timing pulses which coincide in time with the index track pulses (one for each revolution of the drum) are not applied to the counter, a precession effect is obtained whereby if, e.g., addresses 16, 17, &c. were selected during the first drum revolution, addresses 32, 33, &c. would be selected during the second and so on, all the addresses on the drum being thus made available in turn. The address-selecting circuits shown in block diagrammatic form in Figs. 32a-32d (of which circuit details are given in the Specification), consist primarily of crosscoupled double triodes forming bi-stable trigger circuits T and single-shot multivibrators SS, triode inverting circuits I, diode AND and OR pulse-gating circuits, and drum-selecting relay circuits. Reference is made to the use of a magnetic disc or tape in place of a drum. Drum and head construction.-The drum 20, Fig. 1, is wound with cunife wire providing the required magnetic surface, and its shaft 21 is rotated by a motor (not shown) through a belt- and-pulley drive. The read-write heads 28, one for each of the 78 tracks (2 space), are mounted in staggered formation in a drum housing 31. Each head, Fig. 2, comprises a laminated core 30 on which the read and write coils 29 are mounted, and a terminal plug with prongs 34, this assembly being mounted by an adjustment nut 33 in a block 32. The gap between the drum 20 and head 28 is between 0.5 and 2 mils. Read operation.-The Read Drum Select Instruction will cause line 95, Fig. 32c, and one of the lines 94a-94d, corresponding to the required drum, to be marked with positive potentials, thus priming AND gates 142 and 155, Figs. 32c and 32a, through gates 139, 136 and 138 and lines 141, 141a, and operating drum selector and relay switching circuits whereby the reading heads SH, IH, Fig. 32d, associated with the sync and index tracks for the required drum are connected to pulse-amplifying and shaping circuits 187, 188 and 173, 174, the index pulse being also lengthened in single shot multivibrator 176. The timing and index pulses thus obtained are applied to lines 135, 130 respectively, Figs. 32d and 32a. The Set Drum Instruction primes gates 86, 88 through line 86a, whereby at fixed times during the " Execute-Regenerate " portion of the main machine cycle, pulses will be applied through gate 61 and inverter 62 to line 64 and through inverter 91 to line 58. The pulse on 64 is applied to the drum counter 35-45, Fig. 32b, assumed to be reset to zero; the connections, through cathode followers, between successive triggers are such that the counter acts subtractively so that this pulse will set all the triggers to " I." The pulse on 58 is applied to gates 47-57 connecting the counter triggers to corresponding triggers in the address register, to cause a switching to " 0 of those counter triggers for which " 0 is registered in the corresponding address triggers. If no Set Drum signal is provided, the number in the address register will not be transferred to the drum counter, and the zero address will be selected. The Copy Instruction provides a signal on line 148, Fig. 32c, which passes through the gate 142 and, after a delay determined by single-shot multivibrator 145, sets a trigger circuit 147 which in turn sets a trigger circuit 151. The resultant positive potential on line 153 is applied to gate 155, Fig. 32a, to allow the next index pulse on 130 to set trigger 160; the resultant positive potential on line 123 allows the timing pulses on 135 to pass through gate 134 (which gate is, however, inhibited through inverter 131 by the index pulse) to gate 61 and the drum counter input line 64. When the counter is stepped to zero, carry pulses will be obtained from AND circuits 65 and 67, Fig. 32b, which pulses are applied to AND gate 72 to produce a " true end carry pulse on line 78 which is passed through gate 79 (opened by the positive potentials on lines 123, 153) to set a trigger 83 which opens a gate 73, and is also passed through gate 80 to line 82a, Figs. 32b and 32c. The positive potentials on lines 95 (read drum select), 123 and 124 (" copy " trigger 147), allow this pulse to control gates 122, 355a, and a pulselengthening multivibrator 356, to produce a " drum read gate " signal (C, Fig. 5e) on line 126, Figs. 32c and 32d. This allows a timing pulse (A, Fig. 5e) delayed in electromagnetic delay line 196 (B, Fig. 5e) to pass from line 198a through gate 205 (D, Fig. 5e) and trigger a multivibrator 207 whose output (E, Fig. 5e) controls a " peaker " 208 which produces a drum read sample pulse (F, Fig. 5e) applied to gates such as 215, one for each of the 36 storage tracks. The drum selector circuits cause the read coils for the storage tracks of the required drum to be connected via amplifiers such as 224a and squaring inverters such as 225 to the gates such as 215, so that if a " 1 " is read from any of the tracks the squared and inverted amplifier output (G and H, Fig. 5e) will permit the sample pulse to pass through the corresponding gate and set a trigger such as 226 (J and K, Fig. 5e). These triggers form a drum register for temporarily storing the binary number read from the selected drum. Accompanying the signal on line 126, Figs. 32c and 32d, is a signal on line 126a which, through gate 294 and line 296, initiates the following operations controlled by sequentially operated singleshot multivibrators 297, 301, 303:-the resetting of " copy " trigger 147 via line 299; the production of a signal on line 305a which is sent via gate 306 and line 308 to the main machine to control an MQ register (not shown); the resetting of the drum register via lines such as 312 whereby signals are applied to input/output lines 228 to transfer the read number to the MQ register; and the production of a " drum copy proceed signal on line 313 which permits a further " copy " signal to be sent to line 148, if required. If such a signal is sent, trigger 147 is again set and when a " middle carry " is obtained from circuit 65, Fig. 32b, it is passed through gates 73 and 80 to line 82a to produce a further drum read gate signal on line 126, Fig. 32c, to cause a further number to be read from the drum. Reading continues in this manner, once for every 128 pulses applied to the drum counter, until a " copy " signal is no longer provided when the carry pulse on line 82a will control gates 355a, 354 and multivibrator 356 so as to produce a reset signal on line 360 which is passed to line 59, Fig. 32b, to reset the drum counter and trigger 83, and to line 162 to reset trigger 151, Fig. 32c, which in turn resets trigger 160, Fig. 32a. The reset signal is sent also as a " drum disconnect " signal, Fig. 32d, to the Main Machine. Write Operation.-This is similar to the read operation except that the Write Drum Select Instruction will produce a positive potential on line 105, Fig. 32c, in place of 95, so as to render gate 127 operative in place of 122. A drum counter carry pulse will therefore produce a " drum write gate " signal on line 129 which allows a delayed timing pulse on the line 198a, Fig. 32d, to.pass throu