Computer - Random Access Memory (RAM)

What is RAM (Random Access Memory)?

RAM is a computer's volatile memory which stores data temporarily; once power turned off, the data which is inside the RAM gets erased. It is also known as primary or temporary memory. RAM stores the data that is actively being used during the execution of a program or instructions. During the booting process of a system, the operating system actively uses RAM and applications that are necessary to execute a file or a program. It speeds up CPU processing by providing fast data and instruction access.

RAM is actively used for program or instruction execution. Once we start the computer; system necessary files, programs and operating system files are loaded into the RAM for the smooth running of the computer. The more RAM a computer has, the better it can handle multitasking and the faster it can run applications since data can be accessed more quickly.

How does RAM Work?

RAM consists of a grid of cells, each with a unique address, allowing data to be read or written in any order, the CPU requests data from RAM, which is delivered at high speed, making it essential for multitasking and running complex applications.

RAM is the computer's internal memory which stores different types of data and information as per the requirement. It is also considered as read/write memory. The data access in RAM is random. This means that we can access any random location in the memory without even knowing the address of the previous location. Since RAM is a volatile memory hence, a backup is present in most of the systems in the form of an uninterrupted power supply (UPS). Moreover, the speed and performance of a system are directly proportional to the size of the RAM.

Characteristics of RAM

Key Characteristics of RAM are described below −

Multitasking − RAM does multitasking and fast execution of instructions or programs.
Prevents system crashes − RAM prevents system crashes and slowdowns during intensive tasks.
High-performance − It provides high performance for the execution of gaming and visual applications, where large amounts of data must be processed swiftly.
System Support − RAM can perform write and erase operations.
Additional RAM − To maintain the system’s speed and performance; additional RAM can be added on.
Faster data accessing − It facilitates CPU by accessing data quickly to support faster execution. RAM is faster than SSD.
Cost − RAM is not costly as compared to SSD.

Types of Random Access Memory

Different types of RAM are categorised in the below image

SRAM (Static Random Access Memory)

Static RAM is a type of RAM that uses flip-flops for primary storage and is volatile. It is a type of semiconductor memory. Each bit is stored using bistable latching circuitry, making it extremely fast so known as cache memory. It is commonly used as a CPU cache and is typically located in L2 or L3. It stores data in the latch as long as the computer is on. SRAM is more expensive and requires more power than DRAM. It serves as cache memory in a computer system. SRAM requires more transistors than DRAM. It is faster than DRAM because of the latching mechanism. SRAM employs 6 transistors per data bit while DRAM uses one transistor per bit.

Characteristics of SRAM

Some of the key characteristics of SRAM are as follows −

SRAM has a memory cell which consists of 6 transistors.
SRAM consist flip-flop to store data units.
SRAM is dedicatedly designed for the CPU and works as a cache memory.
It accesses data in less time; faster than DRAM, and takes very less time to access data.
Storing a large amount of data on a single chip is not possible, so more chips are needed.
SRAM is expensive.
It requires a regular power supply to store data.
SRAM generates more heat.
Contents remain as it is until power is ON.

Types of SRAM

SRAM can be further classified into the following types −

Synchronous − Synchronous SRAM works jointly with a clock signal. It reads and writes in sync with the clock, making it faster and suitable for high-speed applications.
Asynchronous − Its working is not dependent on the clock signal; it carries out read-and-write operations once the addresses and control signals are stable.
Pseudo SRAM − PSRAM is a type of memory that has features of both DRAM and SRAM. The device uses a DRAM cell but includes an internal refresh circuit, so presenting itself as SRAM to the external system.
Non-Volatile SRAM − nvSRAM integrates a small non-volatile memory with SRAM cells to keep data even when power is off.

Advantages of SRAM

The advantages of SRAM are as follows −

SRAM is preferred because it is much faster.
It does not require being refreshed.
It delivers faster read and write operations.
It works as a cache memory in CPUs.
It is less prone to errors and data corruption caused by the refresh process.
It is very reliable and therefore is used for cache memory.

Disadvantages of SRAM

Disadvantages of DRAM are as follows −

It is expensive.
It has a complex cell structure; so the design and layout of SRAM are more complex.
Due to its volatile nature, overall data is lost when power goes off.
It has a low storage capacity as compared to DRAM.
The design is complex and not easy to build or understand.
It is not Suitable for Large Memory Applications

Overall, speed and reliability make SRAM highly-priced, particularly for applications such as CPU caches. However, its higher cost and lower density compared to DRAM restrict its use to smaller, high-performance memory applications.

DRAM (Dynamic Random Access Memory)

It is another type of RAM used as main memory; it stores data in capacitors for a short period (a few milliseconds) even when the computer is powered on. Each memory cell is a DRAM chip that contains one bit of data and is composed of transistors and capacitors. In this memory controller, the data can be read and then rewritten, constantly updating it. The data is refreshed regularly to ensure its integrity. The DRAM is less expensive, but it can store significantly more data. In addition, it is slower and requires less power than SRAM.

However, DRAM is less expensive than SRAM, making it suitable for use as the CPU's main memory. It is slower than SRAM and can link directly to the CPU bus. A DRAM typically ranges from 4GB to 16GB for laptops and 1GB to 2GB for smaller devices.

Characteristics of DRAM

Some of the key characteristics of DRAM are as follows −

It works as a main memory for the system.
It is made up of capacitors that store the data, thus we need to refresh it multiple times.
It is inexpensive so DRAM is mostly available in Laptops or PCs today.
It requires less space and less power.
It refreshes every millisecond to maintain data consistency.
It is more power-efficient than SRAM.
DRAM can store multiple bits on a single chip.

Types of DRAM

DRAM can be further classified into the following types −

SDRAM − Synchronous with bus clock; general computing.
DDR SDRAM − it has higher data transfer rates compared to SDRAM.
DDR2 SDRAM − It has higher speeds, lower power consumption, and enhanced latency.
GDDR − It is optimized for graphics processing units (GPUs).
LPDDR − It is dedicatedly designed for mobile and embedded applications.
RDRAM − Specifically designed for innovative design for specific high-performance applications.
EDO DRAM − It allows for faster read cycles by overlapping operations.

Advantages of DRAM

The advantages of DRAM are as follows −

DRAM has a slower accessing time than SRAM
Its design is simple, not complex because it consists of only a single transistor.
It is smaller in size.
Its cost is low compared to SRAM
It has high congestion rates.
It has a large memory space.
It has a high density that makes it suitable for large memory applications.

Disadvantages of DRAM

Disadvantages of DRAM are as follows −

It is volatile so continuous refreshing requires keeping data consistent.
Its manufacturing process is complex.
It is slower than SRAM.
It has higher latency compared to SRAM.

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