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(New page: Jump to: navigation, search Computer memory types Volatile * DRAM, e.g. DDR SDRAM * SRAM * Upcoming o Z-RAM o TTRAM * Historical o William...)
 
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Proposals using microfluidic bubbles as logic (rather than memory) have been recently proposed by MIT researchers. The bubble logic would use nanotechnology and has been demonstrated to have access times of 7 ms, which is faster than the 10 ms access times that present hard drives have, though it is slower than the access time of traditional RAM memory and of traditional logic circuits, making the proposal not commercially practical at present. [1]
 
Proposals using microfluidic bubbles as logic (rather than memory) have been recently proposed by MIT researchers. The bubble logic would use nanotechnology and has been demonstrated to have access times of 7 ms, which is faster than the 10 ms access times that present hard drives have, though it is slower than the access time of traditional RAM memory and of traditional logic circuits, making the proposal not commercially practical at present. [1]
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Jump to: navigation, search
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Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetised medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. As of 2007, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the term magnetic storage is preferred and in the field of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference.
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Contents
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[hide]
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* 1 History
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* 2 Technical details
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o 2.1 Access method
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* 3 Current usage
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* 4 Future
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* 5 See also
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* 6 External links
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  +
[edit] History
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  +
Magnetic storage was first suggested by Oberlin Smith in 1888. The first working magnetic recorder was invented by Valdemar Poulsen in 1898. Poulsen's device recorded a signal on a wire wrapped around a drum. In 1928, Fritz Pfleumer developed the first magnetic tape recorder. Early magnetic storage devices were designed to record analog audio signals. Modern magnetic storage devices are designed for recording digital data.
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In early computers, magnetic storage was also used for primary storage in a form of magnetic drum, or core memory, core rope memory, thin film memory, twistor memory or bubble memory. Also unlike modern computers, magnetic tape was often used for secondary storage.
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[edit] Technical details
  +
  +
[edit] Access method
  +
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Magnetic storage media can be classified as either sequential access memory or random access memory although in some cases the distinction is not perfectly clear. In the case of magnetic wire, the read/write head only covers a very small part of the recording surface at any given time. Accessing different parts of the wire involves winding the wire forward or backward until the point of interest is found. The time to access this point depends on how far away it is from the starting point. The case of ferrite-core memory is the opposite. Every core location is immediately accessible at any given time.
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  +
Hard disks and modern linear serpentine tape drives do not precisely fit into either category. Both have many parallel tracks across the width of the media and the read/write heads take time to switch between tracks and to scan within tracks. Different spots on the storage media take different amounts of time to access. For a hard disk this time is typically less than 10 ms, but tapes might take as much as 100 s.
  +
  +
[edit] Current usage
  +
  +
As of 2007, common uses of magnetic storage media are for computer data mass storage on hard disks and the recording of analog audio and video works on analog tape. Since much of audio and video production is moving to digital systems, the usage of hard disks is expected to increase at the expense of analog tape. Digital tape and tape libraries are popular for the high capacity data storage of archives and backups. Floppy disks see some marginal usage, particularly in dealing with older computer systems and software. Magnetic storage is also widely used in some specific applications, such as bank checks (MICR) and payment cards (mag stripes).
  +
  +
[edit] Future
  +
  +
A new type of magnetic storage, called MRAM, is being produced that stores data in magnetic bits based on the GMR effect. Its advantage is non-volatility, low power usage, and good shock robustness. However, with storage density and capacity orders of magnitude smaller than e.g. an HDD, MRAM is a niche application for situations where small amounts of storage with a need for very frequent updates (>10**15 writes) are required, which flash memory could not support

Revision as of 11:38, 20 November 2007

Jump to: navigation, search

Computer memory types Volatile

   * DRAM, e.g. DDR SDRAM
   * SRAM
   * Upcoming
         o Z-RAM
         o TTRAM
   * Historical
         o Williams tube
         o Delay line memory

Non-Volatile

   * ROM
         o PROM
         o EAROM
         o EPROM
         o EEPROM
         o Flash memory
   * Upcoming
         o FeRAM
         o MRAM
         o PRAM
         o SONOS
         o RRAM
         o NRAM
   * Historical
         o Drum memory
         o Magnetic core memory
         o Bubble memory

Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles, which each store one bit of data. Bubble memory started out as a promising technology in the 1970s, but failed commercially as hard disk prices fell rapidly in the 1980s. Contents [hide]

   * 1 Prehistory: Twistor memory
   * 2 Magnetic bubbles
   * 3 Commercialization
   * 4 Further applications
   * 5 External links

[edit] Prehistory: Twistor memory

Bubble memory is largely the brainchild of a single person, Andrew Bobeck. Bobeck had worked on many kinds of magnetics-related projects through the 1960s, and two of his projects put him in a particularly good position for the development of bubble memory. The first was the development of the first magnetic core memory system driven by a transistor-based controller, and the second was the development of Twistor memory.

Twistor memory was based on magnetostriction, an effect which can be used to move magnetic fields. If you place a pattern on a medium (for instance, magnetic tape) and then pass a current through the tape, the patterns will slowly be "pushed" down the tape while the patterns themselves will remain unchanged. By placing a detector at some point over the tape, the fields will pass under it in turn without any physical motion. In effect it is a non-moving version of a single track from a drum memory. In the 1960s AT&T had used Twistor in a number of applications.

[edit] Magnetic bubbles

In 1967 Bobeck joined a team at Bell Labs and started work on improving Twistor. He thought that if he could find a material that allowed the movement of the fields easily in only one direction, a sort of 2D Twistor could be constructed. Patterns would be introduced at one edge of the material and pushed along just as in Twistor, but since they could be moved in one direction only, they would naturally form "tracks" across the surface, increasing the areal density.

Starting with work on orthoferrite, Bobeck noticed an additional interesting effect: if an external field was applied to a magnetized patch of the material, the magnetized area would contract into a tiny circle, which he called a bubble. These bubbles were much smaller than the "domains" of normal media like tape, which suggested that very high densities were possible.

It took some time to find the perfect material, but they discovered that garnet turned out to have the right properties. Bubbles would easily form in the material and could be pushed along it fairly easily. The next problem was to make them move to the proper location where they could be read back out – Twistor was a wire and there was only one place to go, but in a 2D sheet things would not be so easy. The solution was to imprint a pattern of tiny magnetic bars onto the surface of the garnet. When a small magnetic field was applied, they would become magnetized, and the bubbles would "stick" to one end. By then reversing the field they would be attracted to the far end, moving down the surface. Another reversal would pop them off the end of the bar to the next bar in the line.

Five significant discoveries took place at Bell Labs:

  1. The controlled two-dimensional motion of single wall domains in permalloy films.
  2. The application of orthoferrites
  3. The discovery of the stable cylindrical domain
  4. The invention of the field access mode of operation
  5. The discovery of growth-induced uniaxial anisotropy in the garnet system and the realization that garnets would be a practical material.

The bubble system cannot be described by any single invention, but in terms of the above discoveries. Andy Bobeck was the sole discoverer of (4) and (5); he was the co-discoverer of (2) and (3); and (1) was performed in Bobeck's group under his direction and with many significant inputs from Andy. At one point, over 60 scientists were working on the project at Bell Labs, many of whom have earned recognition in this field. In September 1974, for instance, H.E.D. Scovil, working at Bell Labs in New Jersey, was awarded the IEEE Morris N. Liebmann Memorial Award by the IEEE with the following citation: For the concept and development of single-walled magnetic domains (magnetic bubbles), and for recognition of their importance to memory technology.

A memory device is formed by lining up tiny electromagnets at one end with detectors at the other end. Bubbles written in would be slowly pushed to the other, forming a sheet of Twistors lined up beside each other. Attaching the output from the detector back to the electromagnets turns the sheet into a series of loops, which can hold the information as long as you like.

Bubble memory is a non-volatile memory. Even when power was removed, the bubbles remained, just as the patterns do on the surface of a disk drive. Better yet, bubble memory devices needed no moving parts: the field that pushed the bubbles along the surface was generated electrically, whereas media like tape and disk drives required mechanical movement. Finally, because of the small size of the bubbles, the density was theoretically much higher than existing magnetic storage devices. The only downside was speed; The bubbles had to cycle to the far end of the sheet before they could be read.

[edit] Commercialization

Bobeck's team soon had 1 cm square memories that stored 4,096 bits, the same as a then-standard plane of core memory. This sparked considerable interest in the industry. Not only could bubble memories replace core, but it seemed that they could replace tapes and disks as well. In fact, it seemed that bubble memory would soon be the only form of memory used in the vast majority of applications, with the high-speed market being the only one they couldn't serve. Intel 7110 magnetic-bubble memory module Intel 7110 magnetic-bubble memory module

By the mid-1970s practically every large electronics company had teams working on bubble memory. By the late 1970s several products were on the market, and Intel released their own 1 megabit version, the 7110. In the early 1980s, however, bubble memory became a dead end with the introduction of higher-density, faster, and cheaper hard disk systems. Almost all work on it stopped.

Bubble memory found uses in niche markets through the 1980s in systems needing to avoid the higher rates of mechanical failures of disk drives, and in systems operating in high vibration or harsh environments. This application became obsolete too with the development of flash memory, which also brought speed, density, and cost benefits.

One application was Konami's Bubble System arcade video game system, introduced in 1984. It featured interchangeable bubble memory cartridges on a Z80-based board. Games available for the system included Galactic Warriors, Gradius, Konami RF2 (a racing game, also known as Konami GT), and TwinBee. The Bubble System required a "warm-up" time of about 20 seconds (prompted by a timer on the screen when switched on) before the game was loaded, as bubble memory needs to be heated to around 30 to 40 °C to operate properly. The Bubble System did not prove popular, and many games originally available on the system were later released on other arcade boards with conventional ROM chips.

Sharp used bubble memory in their PC 5000 series, a laptop-like portable computer from 1983.

[edit] Further applications

Proposals using microfluidic bubbles as logic (rather than memory) have been recently proposed by MIT researchers. The bubble logic would use nanotechnology and has been demonstrated to have access times of 7 ms, which is faster than the 10 ms access times that present hard drives have, though it is slower than the access time of traditional RAM memory and of traditional logic circuits, making the proposal not commercially practical at present. [1] Jump to: navigation, search

Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetised medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. As of 2007, magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the term magnetic storage is preferred and in the field of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference. Contents [hide]

   * 1 History
   * 2 Technical details
         o 2.1 Access method
   * 3 Current usage
   * 4 Future
   * 5 See also
   * 6 External links

[edit] History

Magnetic storage was first suggested by Oberlin Smith in 1888. The first working magnetic recorder was invented by Valdemar Poulsen in 1898. Poulsen's device recorded a signal on a wire wrapped around a drum. In 1928, Fritz Pfleumer developed the first magnetic tape recorder. Early magnetic storage devices were designed to record analog audio signals. Modern magnetic storage devices are designed for recording digital data.

In early computers, magnetic storage was also used for primary storage in a form of magnetic drum, or core memory, core rope memory, thin film memory, twistor memory or bubble memory. Also unlike modern computers, magnetic tape was often used for secondary storage.

[edit] Technical details

[edit] Access method

Magnetic storage media can be classified as either sequential access memory or random access memory although in some cases the distinction is not perfectly clear. In the case of magnetic wire, the read/write head only covers a very small part of the recording surface at any given time. Accessing different parts of the wire involves winding the wire forward or backward until the point of interest is found. The time to access this point depends on how far away it is from the starting point. The case of ferrite-core memory is the opposite. Every core location is immediately accessible at any given time.

Hard disks and modern linear serpentine tape drives do not precisely fit into either category. Both have many parallel tracks across the width of the media and the read/write heads take time to switch between tracks and to scan within tracks. Different spots on the storage media take different amounts of time to access. For a hard disk this time is typically less than 10 ms, but tapes might take as much as 100 s.

[edit] Current usage

As of 2007, common uses of magnetic storage media are for computer data mass storage on hard disks and the recording of analog audio and video works on analog tape. Since much of audio and video production is moving to digital systems, the usage of hard disks is expected to increase at the expense of analog tape. Digital tape and tape libraries are popular for the high capacity data storage of archives and backups. Floppy disks see some marginal usage, particularly in dealing with older computer systems and software. Magnetic storage is also widely used in some specific applications, such as bank checks (MICR) and payment cards (mag stripes).

[edit] Future

A new type of magnetic storage, called MRAM, is being produced that stores data in magnetic bits based on the GMR effect. Its advantage is non-volatility, low power usage, and good shock robustness. However, with storage density and capacity orders of magnitude smaller than e.g. an HDD, MRAM is a niche application for situations where small amounts of storage with a need for very frequent updates (>10**15 writes) are required, which flash memory could not support