Random Access Memory
From Saferpedia
RAM (Random Access Memory) is that memory randomly readable and writable so there is accessed a single cell of the memory. RAM is the work memory of the PC being used to temporary process the data after which is necessary the data to be saved on a support independent regarding the power supply for maintaining the information.
RAM is a electronic device (component of a computer) to store data. There are found as integrated circuits and allow data storage so they're accessed in any order (random).
RAM memories are volatile meaning they lose their information if they are disconnected from the power supply (on restart or shutdown).
>==History== Old types of RAM, very spread, were the memories with magnetic core developed between 1949 - 1952. They were used until late 60s and early 70s. Before these computers used repeaters, delay line memory or different types of vacuum tubes to fulfill the function of main memory.
Before the ROM (Read Only Memory) integrated circuits development this kind of memories were designed using matrix of semiconductor diodes accessed trough address decoders.
Classification
RAM can be divided in two main types:
- static memory or SRAM;
- dynamic memory or DRAM.
Differences between the two types consist of information stability.
- SRAM keeps data for unlimited periods of time until it is rewritten, like a magnetic environment.
- Dynamic memory requests permanent rewriting every few fractions of a second so not to lose information.
SRAM is mostly used as intermediary memory (cache).
DRAM is used in modern PCs first as main work memory.
Most usual DRAM types used in the computer history all designed with the purpose to increase performance:
- Fast Page Mode DRAM (FPM DRAM),
- Extended Data Out DRAM(EDO DRAM),
- Burst EDO DRAM(BEDO RAM),
- Rambus DRAM(RDRAM),
- Nowadays are imposed the Synchronous DRAM (SDRAM), with variants:
- Double Data Rate SDRAM(DDR SDRAM) sau DDR1 SDRAM
- DDR2 SDRAM
- DDR3 SDRAM
Advantages and disadvantages
Advantages of SRAM: increase utility thanks to operating mode and high speed. Disadvantages: higher price in report with DRAM memories.
This term is in development.
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