Random Access Memory – SRAM , DRAM & DDR

A random access memory (random access memory, RAM) also known as ” RAM “, is CPU exchange data directly to the internal memory , also called the main memory (RAM). It can read and write at any time, and very fast, usually as a temporary data storage medium for the operating system or other running programs.

The content of a storage unit can be arbitrarily removed or stored as needed and accessed at a speed independent of the location of the storage unit.

This kind of memory will lose its storage content when power off, so it is mainly used for storing programs used for a short time.

According to the working principle of the storage unit, the random access memory is further divided into a static random access memory (SRAM) and a dynamic random access memory (DRAM).

SRAM
The static memory cell is constructed by adding a gating transistor to the static flip-flop. Therefore, it is based on the self-preservation function of the trigger to store data.

Dynamic Random Access Memory (DRAM) The
Dynamic RAM memory matrix consists of dynamic MOS memory cells. The dynamic MOS memory cell utilizes the gate capacitance of the MOS transistor to store information, but because of the small capacitance of the gate capacitance and the fact that the leakage current can not be absolutely equal to zero, the charge storage time is limited. In order to avoid the loss of stored information, the capacitor must be regularly filled with missing charge. This operation is usually referred to as “refresh” or “regeneration”, so DRAM internal refresh control circuit, its operation is also more complex than static RAM. In spite of this, DRAM memory cells have become the mainstream products for large-capacity RAM because of their simple structure, low component count and low power consumption.

DDR

Double data rate fourth generation synchronous dynamic random-access memory, is a type of synchronous dynamic random-access memory (SDRAM) with a high bandwidth (“double data rate”) interface.

 

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