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Magnetoresistive RAM

Justin Thompson’s. Magnetoresistive RAM . Overview. What is MRAM? How does it work? Read Write Uses Pros Cons. What is MRAM?. A method of storing data bits using magnetic charges instead of electrical charges used by DRAM

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Magnetoresistive RAM

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  1. Justin Thompson’s Magnetoresistive RAM

  2. Overview • What is MRAM? • How does it work? • Read • Write • Uses • Pros • Cons

  3. What is MRAM? • A method of storing data bits using magnetic charges instead of electrical charges used by DRAM • Magnetoresistive metal-shows slight change in electrical resistance when placed in a magnetic field

  4. What does it look like? • Formed from two ferromagnetic plates that can each hold a magnetic field, separated by a thin insulating layer • One plate is permanently set to a particular polarity • The other plate changes to match that of an external field • A memory unit is made up of a grid of these cells

  5. Reading • Measure the electrical resistance of a cell • A cell is selected by switching the current from a supply line through the cell to ground • Electrical resistance changes due to the orientation of the fields in the two plates • Same polarity = 0 • Opposite polarity = 1

  6. Writing-Conventional • Each cell lies between a pair of write lines that are perpendicular to each other • When current is passed through them, and induced magnetic field is created at the junction • Induced field can overlap adjacent cells, causing false writes(half-select problem)

  7. Writing-Toggle Mode • Multi-step write with a modified multi-layer cell • Magnetic orientation alternates back and forth • Time the write currents to one being slightly delayed from the other to toggle states • Any voltage less than the full write level will increase it’s resistance to flipping • Prevents the half-select problem, allowing for smaller cell sizes

  8. Writing-Spin-torque Transfer • Uses spin aligned electrons to directly torque the domains • If electrons have to change their spin, then this will develop a torque that will transfer to the nearby layer

  9. Pros • Combines the density of DRAM with the speed of SRAM and the non-volatility of Flash • Faster access of data while using low battery power • Doesn’t need to be refreshed • Doesn’t suffer from degradation like Flash • Can operate at high temperatures • Radiation-resistant

  10. Cons • Still being developed • Half-select problem from conventional writing • Cost

  11. Uses • Prevent data loss and enable computers that start instantly without waiting for software to boot up • Help Vista start up faster

  12. Other Interesting RAM • Phase Change Memory-functions based on the reversible phase change between amorphous and crystalline phases of chalcogenidematerials • Ferroelectric RAM-is a memory technology in which the switching occurs by the alteration of the polarization state of a ferroelectric material very quickly and the switching time is of the order of a few nanoseconds.

  13. Conclusion • The high speed and high density of MRAM will make it cutting edge and better than conventional memory • Can replace both memory and hard disk drive • Unfortunately, it is still in development and has high cost • PCs and laptops can startup faster than before

  14. Questions?

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