New Publications are available for Storage on stationary magnetic media
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New Publications are available now online for this publication.
Please follow the links to view the publication.The credit card as a mass storage medium
http://dl-live.theiet.org/content/conferences/10.1049/ic_19951194
Current credit cards store about 140 bytes of information on a magnetic stripe over three tracks. A system has been devised to store and retrieve more than 2 kbytes on a card while maintaining compatibility with current cards. To achieve this a combination of a multi-track read head and new soft decision techniques have been used. (5 pages)Stacking magnetic random access memory atop microprocessors: an architecture-level evaluation
http://dl-live.theiet.org/content/journals/10.1049/iet-cdt.2009.0091
Magnetic random access memory (MRAM) has been considered as a promising memory technology because of its attractive properties such as non-volatility, fast access, zero standby leakage and high density. Although integrating MRAM with complementary metal-oxide-semiconductor (CMOS) logic may incur extra manufacturing cost because of the hybrid magnetic-CMOS fabrication process, it is feasible and cost-effective to fabricate MRAM and CMOS logic separately and then integrate them using 3D stacking. In this work, we first studied the MRAM properties and built an MRAM cache model in terms of performance, energy and area. Using this model, we evaluated the impact of stacking MRAM caches atop microprocessor cores and compared MRAM against its static random access memory (SRAM) and dynamic random access memory (DRAM) counterparts. Our simulation result shows that MRAM stacking can provide competitive instruction-per-cycle (IPC) performance with a large reduction in power consumption.Proposal and experimental demonstration of magnetic tunnel junction connected in parallel with tunnel diode
http://dl-live.theiet.org/content/journals/10.1049/el_20030991
A novel magnetic random access memory cell consisting of a magneto-tunnel junction (MTJ) and tunnel diode connected in parallel is described. The negative differential resistance characteristics of the tunnel diode were used to increase the tunnelling magneto-resistance (TMR) ratio of the MTJ. The fabricated circuit showed that the TMR ratio was enhanced from its original value of 11 to 103%.High cell-efficiency synchronous MRAM adopting unified bit-line cache
http://dl-live.theiet.org/content/journals/10.1049/el_20030783
Unlike the 1T1C cell of the DRAM that suffers the crucial limitation on the bit-line capacitance, the stored information in the couple of the magnetic-tunnel-junction (MTJ) cell is not related to the bit-line capacitance. To achieve the high cell efficiency for the synchronous magneto-resistive random access memory (MRAM), the unified bit-line cache scheme is proposed. It simplifies the column path and provides the low-latency column operations.Processing of inverted files in magnetic-bubble memories
http://dl-live.theiet.org/content/journals/10.1049/ip-e.1984.0013
In this paper the applicability of magnetic-bubble memories to the processing of inverted files is discussed. Four novel models of magnetic-bubble memories are presented to demonstrate storage structures and data processing. The first model employs an organisation of major/minor loops. On the basis of such an organisation a uniform ladder is formed so that the data can be rearranged by using four operations: global shift, detached shift, exchange and delta exchange. The second model makes use of the on-chip decoder (also known as the self-contained magnetic-bubble-memory chip). For this model a hashing scheme is relied upon to perform the required data operations. The third and fourth models are different combinations of the former two models. The latter two models provide a relatively-high-speed performance as well as a reasonable system complexity. For each model the algorithms of data retrieval, sorting, deletion, insertion and updating are given. A comparison of the four models has been carried out in order to determine the most convenient magnetic-bubble-memory structure for the processing of inverted files.Content-addressable memories based on magnetic-domain logic
http://dl-live.theiet.org/content/journals/10.1049/piee.1973.0265
The paper proposes the implementation of logic into magnetic-bubble memories, and particularly the realisation of a content-addressable data storage. The basic bubble-interactive logic and flip-flop functions are briefly reviewed. This is followed by the discussion of the most suitable memory structure and of the logical requirements for content addressing. Two cellular bubble logic-in-memory arrays and their operation modes are described in some detail. One employs successive, the other simultaneous, data access. A comparison between these two designs and a similarly structured random-access bubble memory device is given with special consideration for bit packaging density, interface terminals and data-access time.Magnetic bubbles and their applications
http://dl-live.theiet.org/content/journals/10.1049/ree.1972.0075
Magnetic bubble domains may be formed in platelets of certain magnetic materials. They are the basis for an unusual new breed of devices in which bubbles are selectively created, propagated, interacted, detected and annihilated, so that both memory and logic functions may be performed in a single piece of material. Bubble devices are very compact and dissipate little energy. This paper describes the nature of magnetic bubbles, and the materials which support them. Various aspects of device technology are introduced, with discussion of all the functions required, including bubble interaction logic. Applications for bubble devices are indicated.A cellular array which represents the inertial motions of objects
http://dl-live.theiet.org/content/journals/10.1049/ree.1971.0179
Arrays of identical, uniformly connected circuits are described, which can represent the inertial motions of a group of objects. The objects are represented by ‘object words’, which are propagated within a planar array. Applications for traffic control systems, image-processing and artificial intelligence are proposed.Magnetic bubble domain memories in epitaxial garnet films
http://dl-live.theiet.org/content/journals/10.1049/ree.1975.0143
This paper describes the use of magnetic bubble domains in garnets for computer memory applications. Requirements for computing machine memories are reviewed. Magnetic bubble domain memory technology is described, including bubble domain generation, propagation, and detection. No single garnet composition gives the desired combination of high mobility, useful bubble domain size, and low sensitivity to temperature and bias field. Prototype devices have been constructed which operate routinely at 0.1 MHz data rates. Preliminary estimates of reliability suggest a potential mean time between failures of the order of 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">11</sup> hours.A review of magnetic bubble memories and their applications
http://dl-live.theiet.org/content/journals/10.1049/ree.1981.0014
Interest in magnetic bubble memory technology has increased enormously over the past year. The levels of activity and investment have reached a stage where it can be confidently predicted that 1981 will see their widespread use as digital storage elements in production equipment. This paper reviews what bubbles are, how they work and the architecture of present-day chips. The device manufacturing technology is outlined and some projections made for future advancements in storage density, device price and performance.Applications of bubble memory devices are discussed in terms of the market areas and equipment types for which they are eminently suited. A detailed description of some commercial board level bubble memory systems is given to illustrate the performance achievable as well as design considerations that need to be taken into account in using bubbles. Finally reference is made to end-user equipment and applications that incorporate bubble memories.Domain tip memories
http://dl-live.theiet.org/content/journals/10.1049/ree.1977.0022
Recent domain tip efforts, mainly the DOT memory of CMI and BASF and the MOD memory of TECSI and Crouzet have been directed toward lowering the cost per bit through an increase in the bit density on the substrate and more efficient manufacturing processes. Domain tip memory technology takes advantage of the low cost per bit of the basic magnetic film deposited on a glass substrate despite the lower density as compared to the cost of semiconductors or bubble memory processed substrates.The paper reports mainly on the recent design of MOD which allows unilateral propagation of domains with one level of conductors. Several prototypes in DOT as well as in MOD technologies have been constructed and operated, some of them of a capacity larger than 2 megabits, showing overall error rates better than 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">−9</sup> without correction.Optimizing non-recursive digital filters to non-liner phase characteristics
http://dl-live.theiet.org/content/journals/10.1049/ree.1974.0160
Various methods based on optimization have been used to design linear phase filters. One such method has been to use a general-purpose optimization program to minimize some error criterion, a function of the filter coefficients and of the error between the specified and achieved gain responses. However, if this were to be used with arbitrary phase designs, the error criterion would have to be formulated as a function that combines the gain and phase errors in a meaningful way. It is shaown here that this particular difficulty can be avoided by regarding the phase specification as a deviation from the linear phase and splitting the characteristic into real and imaginary components, rather than gain and phase, and optimizing separately.Electron-beam deflection and registration for information storage
http://dl-live.theiet.org/content/journals/10.1049/el_19690365
An electron-beam-registering system suitable for use with certain types of magnetic store has been devised. Fabrication techniques are discussed and an improved type of system is proposed which will differentiate between positive and negative directions of travel along the <i xmlns="http://pub2web.metastore.ingenta.com/ns/">x</i> and <i xmlns="http://pub2web.metastore.ingenta.com/ns/">y</i> axes.High-speed low-cost read-only memory
http://dl-live.theiet.org/content/journals/10.1049/el_19710435
A high-speed read-only memory is described in which the stored program may be changed easily at low cost. An access time of less than 100 ns has been achieved in an experimental 8192-bit version of the store.Jacoby and Kost's binary two-thirds rate modulation code
http://dl-live.theiet.org/content/journals/10.1049/el_19860791
The state system of this digital magnetic recording code is presented here and was used in simulations of Viterbi decoding to obtain graphs of the bit error rates on the binary symmetric channel and a two-state burst erasure channel. Furthermore, the code's measured power spectral density is also presented.Flash [computer memory]
http://dl-live.theiet.org/content/journals/10.1049/ir_20031108
Ever falling chip geometries are beginning to raise serious doubts as to the long-term viability of flash. Quantum tunnelling is integral to the operation of flash memory, and as chips are getting smaller the ultra-thin tunnelling barrier is becoming increasingly prone to breaking down. A second problem is with the lifetime of flash-based devices, which can be limited to around 100000 cycles. This is fine for some applications, but inadequate where data storage requirements extend over decades. Flash is also quite slow and difficult to program, two problems that are getting more significant as chip areas increase and supply voltages fall. There are three technologies looking to replace flash: magnetic RAM (MRAM), ferroelectric RAM (FRAM) and ovonic RAM. All of these use new materials to create truly nonvolatile memories with long lifetimes. Getting any one of them to replace flash in the marketplace will depend on producing a sufficiently small memory cell, while at the same time minimising the number of additional processing steps required.Ferrite-core unit as combined memory and line scanner in electronic telephone exchanges
http://dl-live.theiet.org/content/journals/10.1049/piee.1970.0372
The paper describes a ferrite-core unit serving both as memory and line scanner in a 64-subscriber electronic telephone exchange used as a p.a.x. (private automatic exchange). This dual function is realised by ferrite cores with a rectangular hysteresis loop, using working points different from those of conventional computer core memories and determined by m.m.f.s produced by currents in the appropriate windings. The cores are arranged in a square matrix and are scanned by a ‘linear-selection’ mode. A special bridge amplifier, with logic-controlled switches in its four arms and the reading winding at its centre, permits the reading currents to be directed as required by actuating a pair of opposite arms.Effects of magnetic keepers on Permalloy-film stores
http://dl-live.theiet.org/content/journals/10.1049/piee.1971.0140
Calculations of magnetic fields and transmission-line reactances have been carried out for the word and sense lines of a thin-film plated-wire store configuration under various conditions of keeper thickness and permeability. Since keeper proximity and thickness shape the applied field distributions, it helps to increase the bit-packing density and affects the word- and digit-driving currents. The induced e.m.f., noise coupling and propagation delays on the line have also been derived. These parameters greatly influence the store performance characteristics, and must be considered in store design.Non-volatile memory characteristics of submicrometre Hall structures fabricated in epitaxial ferromagnetic MnAl films on GaAs
http://dl-live.theiet.org/content/journals/10.1049/el_19930282
Hall-effect structures with submicrometre linewidths (<0.3 μm) have been fabricated in ferromagnetic thin films of Mn<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.60</sub>A<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.40</sub> which are epitaxially grown on a GaAs substrate. The MnAl thin films exhibit a perpendicular remanent magnetisation and an extraordinary Hall effect with square hysteretic behaviour. The presence of two distinct stable readout states demonstrates the potential of using ultrasmall ferromagnetic volumes for electrically addressable, nonvolatile storage of digital information.Bit selection scheme and dipolar interactions in high density precessional MRAM
http://dl-live.theiet.org/content/journals/10.1049/ip-smt_20049037
Precessional switching of the magnetisation is a convenient way to ensure sub-ns, reliable, energy cost efficient writing of an MRAM cell. In this technique, a controlled pulse of magnetic field is applied perpendicular to the easy magnetisation axis of the MRAM cell free layer, which switches the magnetisation from one direction to its reverse. Bit selection and fast direct overwrite can be obtained by superimposing another field pulse along the easy magnetisation axis. It is proposed to change the cell shape while reducing its size to postpone the onset of superparamagnetism. Based on the Landau-Lifshitz-Gilbert equation an analytical theory of this precessional switching process has been developed. This allows the understanding of the minimal switching field and accountingly for the bit selection scheme. A study of how the writing parameter window is affected by a distribution of cell parameters in a array and by the intercell dipolar coupling has been made. A high-pass encoding, and a balanced encoding algorithm are proposed to reduce the maximum intercell dipolar field.Large capacity probe recording using storage robots
http://dl-live.theiet.org/content/journals/10.1049/ip-smt_20030693
The authors propose a concept in mass data storage system architecture, in which thousands of read/write heads, storage robots or StoBots move independently over a large, flat storage medium. This concept, which has not been previously proposed, offers new degrees of freedom in data storage systems design, which could lead to a superior performance over conventional systems such as hard disks and tape. The impact of different file system architectures on the access time and data-rate of the StoBot drive is investigated.Non-volatile run-time field-programmable gate arrays structures using thermally assisted switching magnetic random access memories
http://dl-live.theiet.org/content/journals/10.1049/iet-cdt.2009.0019
This study describes the integration of thermally assisted switching magnetic random access memories (TAS-MRAMs) in field-programmable gate array (FPGA) design. The non-volatility is achieved through the use of magnetic tunnelling junctions (MTJs) in an MRAM cell. A TAS scheme is used to write data in the MTJ device, which helps to reduce power consumption during a write operation in comparison with the conventional writing scheme used in MTJ devices. Furthermore, the non-volatility allows reducing both power consumption and configuration time required at each power-up of the circuit in comparison with classical static random access memory-based FPGAs. An innovative architecture furthermore provides run-time reconfigurable (RTR) support at minimum area overhead. A RTR FPGA element using TAS-MRAM allows dynamic reconfiguration mechanisms, while featuring simple design architecture.