| ext">MRAM chip design (Credit: Freescale) | | | | is suddenly shut off. MRAM has much faster write |
| In early July 2006, Freescale Semiconductor | | | | speeds than Flash and has an unlimited endurance, |
| announced the first commercial availability of a | | | | meaning that MRAM is not subject to the |
| new type of memory with the potential to | | | | degradation suffered by Flash. |
| surpass most existing types in terms of speed, | | | | Conventional RAM memory is made of transistors |
| power consumption, and durability. This article | | | | and capacitors that are paired to create a |
| reviews the advantages of MRAM and its future | | | | memory cell, which represents one bit of data (0 |
| potential. | | | | or 1). Memory cells are aligned in columns and |
| With the continual release in recent years of new | | | | rows, the intersections of which are known as |
| types of computer memory (RAM, ROM, DRAM, | | | | addresses in which information is stored. Reading |
| Flash, SRAM, PRAMÂ…), the memory chip | | | | and writing information occurs by measuring or |
| industry has become an ever more bewildering | | | | changing the charge at a specific address, |
| world. Freescale's MRAM, one of the latest to be | | | | accordingly. |
| commercially unveiled, improves on and combines | | | | MRAM read process - Current is passed through |
| the advantages of two types of conventional | | | | the bit, resistance of the bit is sensed (Credit: |
| memory. | | | | Freescale) |
| The various types of computer memory can be | | | | MRAM works in a different way, more like the |
| classified in several different ways, the simplest of | | | | read/write head of a hard drive. But unlike a hard |
| which is the division into volatile and non-volatile | | | | drive, which includes mechanical parts (the moving |
| memory. Volatile memory requires constant | | | | arm holding the read/write head and the rotating |
| power to maintain stored information. Most types | | | | plates on which the information is stored), MRAM |
| of RAM (random access memory), the most | | | | is a solid state device and, as such, has much |
| common type of memory used by modern | | | | greater speed and durability. Like conventional |
| computers are volatile, Thus, to store information, | | | | RAM, MRAM is composed of transistors but, |
| conventional RAM computer chips are dependent | | | | instead of electrical charges, it uses magnetic |
| upon electricity flowing through them. When the | | | | charges to store information. An MRAM chip is |
| power is switched off (i.e., when the system is | | | | made up of millions of pairs of tiny ferromagnetic |
| "powered down"), unless the information has been | | | | plates (like the one covering hard drives) called |
| copied to the hard drive, the information is lost. | | | | memory cells, i.e., magnetic sandwiches consisting |
| Non-volatile memory, on the other hand, can | | | | of two magnetic layers separated by a very thin |
| retain stored information permanently, absolving | | | | insulating layer. Each magnetic layer has a polarity |
| the need for a constant power supply. ROM | | | | — a north pole and a south pole. These can |
| (read-only memory), which stores information | | | | be oriented in a parallel orientation, meaning that |
| that does not require frequent changing (i.e., | | | | both have their respective poles (or 'magnetic |
| doesn't need rewriting), such as Firmware (a | | | | moments') in the same orientation, or in an |
| software embedded inside a hardware such as a | | | | anti-parallel fashion, meaning that their poles |
| BIOS [basic input-output system]) is typically | | | | magnetic moments are oriented in opposite |
| non-volatile. So, even when the system is off, the | | | | directions. These relative magnetic pole |
| data is stored. | | | | orientations correspond to the binary memory |
| Modern types of ROM such as Flash, used in | | | | states, either 0 or 1. |
| thumb drives and many MP3 players, are also | | | | MRAM write process - Current is passed through |
| non-volatile, but easily rewritable, making them | | | | the programming lines generating magnetic fields. |
| more like RAM. This combination of qualities has | | | | The sum of the magnetic fields from both lines is |
| made Flash memory highly popular in recent years | | | | needed to program the bit. (Credit: Freescale) |
| and it is currently used to improve other types of | | | | An MRAM chip reads information by measuring |
| storage such as hard drives or even replace them | | | | the electrical resistance of a specific cell that, in |
| altogether. But although Flash is cheap and | | | | turn, depends upon the alignment of the magnetic |
| non-volatile, it still suffers from a relatively limited | | | | moments of the layers of the cell. To read a bit |
| lifetime. Though this had improved considerably in | | | | of information, a current is passed through the |
| the last few years, more importantly, Flash still | | | | memory cell. If the magnetic moments are in a |
| has a much lower write speed than RAM. | | | | parallel orientation, then the detected resistance |
| In an attempt to combine the speed of the | | | | would be smaller than if they were in an |
| faster volatile memory with the benefits of | | | | anti-parallel orientation. |
| non-volatile memory, Freescale (which originated | | | | Write is achieved by the alignment of the |
| from Motorola Semiconductor about two years | | | | magnetic moments of the two memory layers |
| ago) created a new type of non-volatile memory | | | | into one or the other relative orientation. Current |
| - Magnetoresistive Random Access Memory, or | | | | is passed through two sets of parallel wires or |
| MRAM. The roots of MRAM can be traced back | | | | write lines (called a bit line and a digit or word line), |
| to the 1940's at Harvard when physicists An | | | | which pass over and beneath the memory cells, |
| Wang and Way-Dong Woo and later Jay | | | | respectively. The bit lines and the digit lines run |
| Forrester and colleagues at MIT worked on | | | | perpendicular to one another and at their |
| developments that led to Magnetic Core Memory | | | | intersections lie the magnetic memory cells, each |
| and later on to the discovery of the "giant | | | | defined by one particular bit line and one particular |
| magnetoresistive effect" in thin-film structures by | | | | digit line. To write to a particular memory cell (bit), |
| researchers from IBM in the late 1980's. Like | | | | current is passed through the two wires that |
| Flash, MRAM retains data after a power supply is | | | | intersect at that memory cell. The magnetic field |
| cut off, potentially eliminating that seemingly | | | | that is generated from current passing through a |
| endless boot time of conventional computers | | | | wire can change the orientation of the magnetic |
| when data from the hard drive is transferred to | | | | moments of the particular memory cell. |
| RAM, as well as loss of data when the computer | | | | |