Types of RAM (Random Access Memory) - Static RAM and Dynamic RAM

Types of RAM (Random Access Memory) – Static RAM and Dynamic RAM

What is RAM?

DefinitionFull form of RAM is “Random Access Memory” in computer industry. It is meaning of RAM that it can access all necessary data and file programs randomly from cache memory, and it is also known as “Primary Memory“, “Main Memory”, “Internal Memory”. RAM is hardware part of computer which is embedded on the motherboard.

In this article, we will be explained RAM and its types in detail.

RAM is volatile nature memory, that means it is capable to store data and instructions while power turning on. When we turn on the computer system then RAM fetches all necessary data and instructions from hard disk, and stored them. CPU uses fetched data by RAM to perform the specific tasks.

Most popular DRAM manufacturers companies are Samsung, Rambus, PNY Technologies and SK Hynix

Read More – Complete Guide to Computer Memory

Uses of RAM

Read More – What is Primary Memory and its Types

RAM is used to perform several activities, Such as –

  • Main motive of using RAM is to store all data, files, programs or operating system that are using in real time for CPU.
  • It allows the fastest operating speed.
  • It provides less power dissipation.
  • It is getting more popularity due to its compatibility.
  • It is able to write, read and delete of all information many number of times.

Types of RAM (Random Access Memory)

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There are two different types of RAM (Random Access Memory), we can say also examples them.

  • Static RAM
  • Dynamic RAM

What is SRAM (Static)?

Read More – Primary Memory vs Secondary Memory

Full form of SRAM is “Static Random Access Memory” in Computer industry.

Definition – Static RAM is able to retain all information into static form until power supply is turn off, so due to this nature this memory is known as volatile memory. Main objective of using the static RAM is to make Cache Memory. Static Ram is more expensive as well as its power consumption more to dynamic RAM, but Static Ram has higher speed compare to dynamic RAM. In S RAM, All data has been stored in flip-flop. Flip-flop contains the every bit of this Ram. Flip-flop uses 4-6 transistors for making a memory cell and its circuit do not need to refreshment continuously.

Example – Unsaved PPT file in PowerPoint and other any unsaved data in the software.

Types of SRAM (Static)

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There are different types of SRAM, such as –

Non-Volatile SRAM

Non-volatile SRAM is capable to store all information when power supply gets turn off.

Pseudo SRAM

Pseudo SRAM uses the self refresh circuit, but it is slow speed to static RAM.

Static RAM is divided into two parts according to its functionality

Asynchronous

In which, Address transition has all control of data in and data out, and it contains the independent of clock frequency.

Synchronous

In which, all control signals, data, and address are linked with the clock signals.

SRAM Circuit Design and Operation

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SRAM cell is designed with two inverters, which are cross-linked like as latch form. This latch is made connection to two bit line along with two transistors T1 and T2. Now both transistors are capable to alter their modes (open or close) under control of word line, and this entire process is controlled by address decoder. When word line goes to ground level then both transistors get turned off, and latch starts to retain own state.

SRAM working

Static RAM working is divided into two parts Read and Write Operation

Read Operation

Both switches T1 and T2 are closed while activating the word line. When, cell comes to state 1 then signal flows in high amount on b line and other side signal flows in low amount on b’ line. Opposite is true when cell goes to state 0. Finally both b and b’ get complement of each other’s.

Sense/write, which are connected in the rear side of two bit line, they monitor their states and finally convert into output respectively.

Write Operation

In the write operation, Sense/Write circuit allows to drive bit lines b and it complement b’, and then it provides accurate values on bit line b and b’ as well as go to activate word line.

Applications and Uses of SRAM

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Static RAM is mostly used in different areas such as –

  • Modern Electronics Equipment
  • Advance Microprocessors
  • Automobile Equipments
  • Computer Cache Memory
  • Digital to Analog Converter on a video card
  • Digital Cameras
  • Cell Phones
  • Synthesizers
  • Toys
  • Routers
  • CPU register files
  • Hard disk buffers
  • Router buffers
  • LCD Screens
  • Printers
  • Networking
  • Aerospace
  • Medical Equipments
  • Computing Applications

Advantages of Static RAM

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There are some benefits of SRAM, such as

  • No require periodically refreshment circuit.
  • Great Performance
  • Good reliability
  • Less idle time during power consumption

Disadvantages of Static RAM

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There are some limitations of SRAM, such as – 

  • Expensive
  • High density
  • More power consumption while performing its tasks.

What is DRAM (Dynamic)?

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MeaningFull form of DRAM in computer industry is “Dynamic Random Access Memory“.

Definition – DRAM is another type of semiconductor memory, and it is designed specially to store data or program files which are needed by computer processors for performing their functions.

In DRAM, several capacitors are used for storing every bit of data. This is very simple path to save data in its memory because it needs small area to store same data to SRAM as well as it is capable to store massive data than to SRAM but it requires the frequently refreshing of its circuit for its charging, so it consumes more power compare to SRAM.

Types of DRAM (Dynamic)

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There are different types of DRAM, and below explain them  

FPM DRAM

FPM DRAM stands for “Fast Page Mode DRAM”, and this DRAM has fast speed to other conventional DRAMs. FPM DRAM mostly used in the personal computers, but today it is not useful because it was only capable to support memory bus speed rate up to 66 MHz.

EDO DRAM

EDO DRAM stands for “Extended Data Out DRAM”, and it had great performance than FPM DRAM but its speed was same FPM DRAM like as 66 MHz.  It performs all processing on the FIFO principle “First Come First Out”. For example Intel Pentium

BEDO DRAM

BED DRAM stands for “Burst EDO DRAM”, and it provided the best performance compare to EDO DRAM. It was able to process 4 memory addresses in single burst so it could save three clock cycle processes. This task was completed with appending one on-chip address counter count the next address.

BEDO DRAM was used the page access cycle with attaching pipeline, and further it classified into two major parts such as –

  1. First part was capable to access all data from memory array to O/P state.
  2. Second part played major role to drive entire data buses from this latch on the specific logic level.

SDRAM

SDRAM stands for “Synchronous Dynamic Access Memory”, and it can access any element of data within 25 to 10 nano second. SDRAM are used in the DIMM (dual in-line memory module) along with 168 contacts.

In which, all data are stored with the help of capacitors using IC’s “Integrated Circuits”, and it is inserted into its specific slot, which is embedded on the motherboard.

ADRAM

Asynchronous DRAM is basic form of the DRAM, and Asynchronous DRAM is enabling to different connections like as power, address inputs, and bidirectional data lines. It controls the timing of all memory devices with asynchronously nature, and memory controller circuit arises the useful control signals to control timing.

RDRAM

RDRAM stands for “Rambus DRAM”, and it was designed by Rambus Inc; especially for graphic card. Now these days, modern RDRAM has higher data transfer rate to CPU memory bus because it includes several new speedup techniques such as synchronous memory interface system, caching enabled DRAM chips and faster signal timing. RDRAM consist 8 or 9 bits width data bus.

CDRAM

CDRAM stands for “Cache DRAM”, and it is designed specially with enabling on-chip cache memory. It works as high speed buffer to main Dynamic RAM.

SDR SDRAM

SDR SDRAM stands for “Single Data Rate synchronous DRAM”, and it can allow only one instruction and transfer one frame of data’s word on per clock cycle. It can bear clock frequency up to 100 to 133 MHz, and it performs all tasks on the 3.3 V voltages. These types of chips are designed with several data buses forms such as 4, 8, or 16 bits, and they are assembled into 168 pin DIMM package module. These chips are capable to read or write with 64 bit concurrently.

DDR SDRAM

DDR SDRAM stands for “Double Data Rate SDRAM”, and it provides the more bandwidth to all users. It is capable to accept the same commands at the once per cycle, and it can transfer double words of data with one clock cycle at a same time. Its clock rates are 133, 166 and 200 MH.

There are some family members of DDR SDRAM

DDR2 SDRAM

It is second member of DDR SDRAM family. It provides the double bus rate on per clock cycle rate, and it uses the different clock rates like as 200, 266, 333 or 400 MHz.

DDR3 SDRAM

It provides the double bandwidth and bus to DDR2 rate on single clock rate. DDR3 is capable to fetch 100-200 M per second, and its clock rate is 400–800 MHz.

DDR4 SDRAM

It has great performance to DDR3 due to use its modern signal processing, and it uses fewer power consumption (1.2 V) along with huge memory capacity. Its clock rate up to 1600MHz as well as enable 288 pin configurations.

DDR5 SDRAM

It enables the double bandwidth to DDR4 while reducing power consumption (1.1 V).

GDDR SDRAM

GDDR SDRAM stands for “Graphics Double Data Rate Synchronous Dynamic RAM”, and it is developed specially for graphics processing units (GPUs). GDDR provides the high definition environment for playing games to users. GDDR has own growing performance family similar to DDR SDRAM such as  GDDR2 SDRAM, GDDR3 SDRAM, GDDR4 SDRAM, and GDDR5 SDRAM.

Types of DRAM Packages

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There are mainly three types of DRAM memory module packages like as –

  • SIMM (Single In-line Memory Module)
  • DIMM (Dual In-line Memory Module)
  • RIMM (Rambus In-line Memory Module)

SIMM (Single In-line Memory Module)

This memory package consist the eight or nine RAM chip, where eight is used in MAC and nine in the personal computer but 9th chip is reserved to parity checking. SIMM used the 32 bit bus width, and it was available in 30 or 72 pin modules.

DIMM (Dual In-line Memory Module)

Now these days, DIMM is used as memory modules because its performance is excellent to SIMM. In DIMM, pins are embedded on the both sides of this module. Some years ago, DIMM was supported 168 pin connectors with 64 bit data bus. But now DIMM works on the latest technology like as fourth generation double data rate (DDR4) SDRAM, and it contains the 288 pin connectors.

Some Common Types of DIMM

UDIMM (Un buffered DIMM)

It is designed specially to use on desktop and laptops because its speed fast and cost effective but not stable.

FB-DIMM (Fully buffered DIMM)

These memory modules are used in large system such as servers and workstations, and it enables the error detection techniques for decreasing the soft errors and bugs.

RDIMM (Registered DIMM)

It is also called the “Buffer” memory, because it is used in the servers and large applications, where to need the more stability and robustness.

LR-DIMM (Load Reduced DIMM)

It is used for decreasing the overload on the main memory controller along with buffering (data and address).

SO-DIMM (Small outline DIMM)

It has small size compare to standard DIMM because these memory modules are used small size PCs such as laptops, PDA and notebooks, etc.

RIMM (Rambus In-line Memory Module)

This memory package is similar as a DIMM but it is known as RIMM because of their manufacture companies slot needed.

SO-RIMM (Small outline RIMM, SO-RIMM)

It is small version of RIMM memory module package.

How Does DRAM Work? With its Operations

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DRAM was invented by Robert Dennard in 1966, at IBM. DRAM uses two elements as a storage cell like as transistor and capacitor. To keep charge or discharge of capacitors to be used the transistor. If logic high or “1” it means capacitor is fully charged otherwise it is discharged then its logic low or “0”. All operations of charging or discharging are performed by work line and bit line. Show in figure.

dram working

There are two functions like as

  • Write operation
  • Reading Operation

Write Operation

In this operation, Voltage is supplied on bit line as well as signal is supplied on the address line for closing the transistor.

Reading Operation

While storing the information on the cell, then transistor is turned on and voltage is supplied for bit line. Due to this process, some charge is stored in the capacitors. After some time transistor is turned off mode, and it goes to discharge. Hence, entire information is stored in the cell which can be read easily.

Applications and Uses of DRAM

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Due to cost efficient storage of DRAM, it is used in several areas such as –

  • It is used in different batteries for synchronous and asynchronous applications.
  • Personal Computers, Laptops,  PDA and more.
  • Digital electronics equipment.
  • Enhance of graphics functions of PCs.
  • Networking Architecture
  • Workstations and Servers

Advantages of DRAM (Dynamic)

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Here, we will spread light on the several characteristics and benefits of dynamic RAM for main memory.

  • DRAM is designed with simple technique because in which use single transistor.
  • It allows the great integration density levels.
  • It is able to store massive data.
  • It is capable to refresh and delete itself while processing.
  • Cost effective
  • Good reliability
  • Very dense
  • Less power consumption
  • It needs small area
  • Low cost per bit

Disadvantages of DRAM (Dynamic)

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There are several limitations of DRAM, such as –

  • Its accessing speed is very slow compare to SRAM.
  • All data is discarded due to power is OFF because it is Volatile memory.
  • It consumes more power to SRAM.
  • Data needs to refreshment continuously.
  • It has complex manufacturing process.

Difference Between SRAM & DRAM

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There are some key points of SRAM Vs DRAM, such as –

Static RAM

  • More expensive.
  • It has excellent speed to DRAM.
  • Use in L1 and L2 Caches Memory.
  • High density, it means six transistors per chip.
  • Volatile Memory – Do not need extra charges for storing data.
  • It is placed between main memory and processor.
  • Linked directly to Cache Memory.
  • Small size
  • Use transistors and latches.
  • It uses six transistors in one block memory.
  • Do not need refreshing circuit.
  • Consume less power to DRAM.
  • SRAM is on chip memory, it needs small access time.

Dynamic RAM

  • Less expensive
  • It has slow speed to SRAM
  • It is used in Main Memory.
  • It uses low density per cell; it means one transistor per chip.
  • Volatile Memory – need regular power supply to store data.
  • It is embedded on the motherboard of PC.
  • It is attached directly with CPU bus.
  • Large size
  • Use capacitors.
  • It uses one transistor in one block memory.
  • Need power refreshing circuit
  • Consume high power.
  • DRAM is off chip memory that means, it needs large access time.

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