17-03-2011, 12:05 PM
SUBMITTED BY
D.SRAVANI
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What is Memory?
CLASSIFICATIONS OF MEMORY:
• Internal Processor Memory
• Main Memory
• Secondary Storage Memory
Memory Device Characteristics:
Cost
Access Time and Access Rate
Access Mode- Random and Serial
Alterability- ROMS
Permanence of Storage:
1) Destructive Read-Out
2) Dynamic Volatility
3) Volatility
Cycle Time and Data Transfer
Limitations of Present Memory Technologies:
Random Access Memory:
Volatile and expensive.
Dynamic RAM:
Volatile and difficult to integrate.
Static RAM:
Expensive.
Erasable-Programmable Read Only Memory:
High Power Requirement, Poor Flexibility.
FLASH:
Limited number of Read and Write cycles
Challenges :
• The ability to retain stored charge for long periods with zero applied or refreshed power.
• High speed of data writes.
• Low power consumption.
• Large number of write cycles
Emerging Memory Technologies:
Supports expansion in 3-dimensional spaces
Fe-RAM:
Data is stored by applying a very low voltage.
Polymer Memory:
Different conductivity states represents bits of information.
NROM:
Stacks are used to store charges which writes into memory.
MRAM:
Data is stored by applying magnetic fields.
OUM
Ovonic Unified Memory:
The OUM is non-volatile memory that uses the reversible structural phase-change in thin-film material (e.g., chalcogenides) as the data storage mechanism.
Electrical energy (heat) is used to convert the material between crystalline (conductive) and amorphous (resistive) phases and the resistive property of these phases is used to represent 0s and 1s.
Once programmed, the memory state of the cell is determined by reading its resistance.