Random Access Memory

Random Access Memory( RAM )

-Is a form of computer data storage.
-Today it takes the form of integrated circuits that allow the stored data to be accessed in any order.
-The word random thus refers to the fact that any piece of data can be returned in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data.

-The word RAM is mostly associated with volatile types of memory (such as DRAM memory modules), where the information is lost after the power is switched off.

-Modern types of writable RAM generally store a bit of data in either the state of a flip-flop, as in SRAM (static RAM), or as a charge in a capacitor (or transistor gate), as in DRAM (dynamic RAM), EPROM, EEPROM and Flash.

5 types of Ram
~ SRAM (Static Ram)
~DRAM (Dynamic Ram)
~SDRAM (Synchronous Ram)
~DDR RAM (Double Data Rate SDRAM)
~SGRAM (Synchronous Graphics RAM)

# SRAM

Static random access memory (SRAM) is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM (DRAM), it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit.

SRAM exhibits data remanence,[1] but is still volatile in the conventional sense that data is eventually lost when the memory is not powered.


# Dynamic random access memory
Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit.
Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically.

Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory.

~SDRAM
SDRAM refers to synchronous dynamic random access memory, a term that is used to describe dynamic random access memory that has a synchronous interface.

Traditionally, dynamic random access memory (DRAM) has an asynchronous interface which means that it responds as quickly as possible to changes in control inputs.

SDRAM has a synchronous interface, meaning that it waits for a clock signal before responding to control inputs and is therefore synchronized with the computer's system bus.

The clock is used to drive an internal finite state machine that pipelines incoming instructions.

~DDR SDRAM
DDR SDRAM (double data rate synchronous dynamic random access memory) is a class of memory integrated circuits used in computers.

It achieves nearly twice the bandwidth of the preceding [single data rate] SDRAM by double pumping (transferring data on the rising and falling edges of the clock signal) without increasing the clock frequency.

Synchronous Graphics RAM (SGRAM)
SGRAM is a specialized form of SDRAM for graphics adaptors. It adds functions such as bit masking (writing to a specified bit plane without affecting the others) and block write (filling a block of memory with a single colour).
Unlike VRAM and WRAM, SGRAM is single-ported. However, it can open two memory pages at once, which simulates the dual-port nature of other video RAM technologies.