Types Of Memory

Types Of Computer Memory

An essential component of the computer is its memory. An essential requirement for a computer is its capacity to remember, assess, and react correctly to user orders. Computer memory refers to any physical part that has the ability to store data either permanently, like ROM, or temporarily, like RAM. Don't think about RAM and ROM for now We will talk about them. Operating systems, software, and hardware all use memory devices that make use of integrated circuits.

When we talk about computer memory devices, they can be classified into two categories.

Types of memory

Ok now think about the human brain, in the day to day life you connect with lots of things, but you don't remember everything you did after a few weeks so we can call it short-term memory, but some things you remember until you die we can say that is long term memory,  

Similar to the human brain, there are different types of memory storage available on the computer. With changing times and constant development in technology, memory is also upgraded.

Before we start I want to tell you, There are a few other memory classifications based on other facts and we will discuss them in detail in future videos.

But in this article, we only focus on primary memory and secondary memory which is based on CPU access.

That means if the CPU can directly connect to the corresponding memory with minimum delay, it is classified as primary memory and if the CPU can not directly connect to the corresponding memory, it is classified as secondary memory.

primary memory

An area of computer memory that can be accessed directly by the CPU is the primary memory, sometimes referred to as internal memory or internal storage. The CPU continuously reads instructions stored there and executes them as required. Primary memory can be either volatile (RAM) or non-volatile (ROM), and accessing data from it is pretty quick. Comparing primary and secondary memory, the capacity of primary memory is limited.

To increase system efficiency, Memory is arranged in the system to reduce the amount of time process to gain access, 

There are two primary memory types RAM and ROM.

 

RAM (Random Access Memory)

RAM (Random Access Memory) is the component of a computing device that stores the operating system (OS), application programs, and data currently in use so that the processor can access them quickly. A computer's main memory is RAM. Compared to other forms of storage like an optical drive, hard disk drive, or solid-state drive, it is much faster to read from and write to the RAM.

It's called random access because the data can be quickly read and modified in any order

It is volatile to memory. so the Data is only stored in RAM as long as the computer is running, but it is erased when the computer is powered off. When you power on the computer The OS and other files are usually reloaded into RAM from an HDD or SSD.

There are two types of Rams.

SRAM & DRAM

1. What exactly is SRAM?

SRAM is a form of semiconductor memory that stores each bit using Bistable latching circuitry. The six transistor memory cell is used to store data in this type of RAM. Static RAM is primarily used as a processor cache memory (CPU).

SRAM is faster than other types of RAM, such as DRAM. It also uses less energy. SRAM stands for Static Random Access Memory.

    2. What exactly is DRAM?

It is a type of RAM that allows each bit of data to be stored in a separate capacitor within a specific integrated circuit. It is a type of computer memory found in most modern desktop computers. DRAM stands for Dynamic Random Access Memory. DRAM is built with capacitors and a few transistors. The capacitor is used to store data in this type of RAM, where bit value indicates that the capacitor is charged and bit value 0 indicates that the capacitor is discharged.

Distinctions between SRAM and DRAM

SRAM	DRAM
It retains data as long as power is supplied.	It stores data for as long as power is supplied or for a few milliseconds after power is turned off.
In SRAM, transistors are used to store data.	Capacitors are used in DRAM to store data.
Because capacitors are not used, no refreshing is needed.	To store information for a longer amount of time, the capacitor's contents must be refreshed on a regular basis.
These are high - priced.	These are less expensive.
SRAMs have a low density.	DRAMs are high-density storage devices.
These are found in cache memory. Some general uses of SRAM include L2 and L3 CPU cache units.	These are found in primary memories.
It uses less energy and produces less heat.	It consumes more energy and produces more heat.
When compared to DRAM, SRAM has a lower access time.	The access time of DRAM is higher. It performs slower than SRAM.
SRAM is smaller in size.	DRAM comes in larger storage capacities.

Cache Memory

A small piece of high-speed volatile memory available to the processor for fast processing is called cache memory. The cache may be a reserved portion of the main memory, another chip on the CPU, or an independent high-speed storage device. Cache memory is made of fast-speed SRAMs. The process of keeping some data and instructions in cache memory for faster access is called caching. Caching is done when a set of data or instructions is accessed again and again.

Whenever the processor needs any piece of data or instructions, it checks the cache first. If it is unavailable there, then the main memory and finally secondary memory are accessed. As the cache has very high speed, time spent accessing it every time is negligible as compared to the time saved if data indeed is in the cache. Finding data or instructions in the cache is called a cache hit.

Cache • Cache is a high-speed access area that can be either a reserved section of main memory or a storage device. • Most computers today come with L3 cache or L2 cache, while older computers included only L1 cache

The RAM in a common computing device is made up of Dynamic Random Access Memory (DRAM), which, as was already said, requires electricity to retain stored data.

An electrical capacitor stores the charge or absence of charge for each DRAM cell. To compensate for leaks from the capacitator, this data must be regularly updated with an electrical charge every few milliseconds. A transistor acts as a gate, deciding whether it is possible to read or write the value of a capacitor.

ROM (read-only memory)

ROM, which stands for read-only memory, is a memory device or storage medium that stores information permanently. It is also the primary memory unit of a computer along with the random access memory (RAM). It is called read-only memory as we can only read the programs and data stored on it but cannot write on it. It is restricted to reading words that are permanently stored within the unit.

The term "read-only memory," or ROM, refers to a memory device or storage media that permanently stores information. Along with the random access memory, it serves as a computer's primary memory. Since we are unable to write to it, read-only memory is used for reading programs and data. It can only read data that have been permanently saved inside the device.

ROM contains special internal electronic fuses that can be programmed for a specific interconnection pattern. Once the pattern (information) is established, it remains in the device even when the power is switched off. As a result, it is a non-volatile memory because it remains the information even after the power is switched off.

If you remember,

Your computer's screen does not immediately appear when you turn it on. It takes some time to load because there are startup instructions stored in ROM which are required to start the computer during the booting process. It is a procedure that begins as soon as the computer is turned on and ends after the operating system has been loaded into memory. The computer's CPU uses the BIOS program, which is also contained in the ROM, to start the computer when it boots up. It connects the computer to the operating system and enables you to access the machine.

Small programs called firmware are also stored in ROM, and they contain instructions the computer can use in performing some of the most basic operations required to operate hardware devices.

At the time of ROM manufacturing, the manufacturer loads the programs into the ROM. After then, the ROM's content cannot be changed, meaning it cannot later be programmed, rewritten, or erased. But there are some ROM types, where the data can be changed.

ROM-types

MROM-Mask ROM (MROM) chips contain a software mask that is burned onto the chip during the design phase of the semiconductor manufacturing process. Mask ROM (MROM) chips are used in computer systems that require long-term sustainability.

PROM-PROM or programmable ROM (programmable read-only memory) is a computer memory chip that can be programmed once after it is created. Once the PROM is programmed, the information written is permanent and cannot be erased or deleted.

EPROM-EPROM (erasable programmable read-only memory) is programmable read-only memory (programmable ROM) that can be erased and reused. Erasure is caused by shining an intense ultraviolet light through a window that is designed into the memory chip

EEPROM-EEPROM stands for Electrically Erasable Programmable Read-Only Memory. It is a memory chip that we can erase and reprogram using an electrical charge. It consists of a collection of floating gate transistors. Flash memory is a type of EEPROM that has a higher density and lower number of write cycles.

Secondary memory

Secondary memory is persistent, non-volatile computer memory that a processor cannot access directly. Data that can be quickly and easily retrieved, transmitted, and used by applications and services to store data permanently.

All permanent or persistent storage devices, including magnetic tapes, hard disk drives (HDD), flash drives, and other internal and external storage media, are considered secondary memory. Only the primary or main memory can access secondary memory during computations, and only then is it sent to the processor.

Even if the computer is not powered on, data is retained in secondary memory and it is slower than primary memory. Additionally, it has large storage capabilities, with each unit having a few megabytes and several terabytes of storage space.

These are some characteristics of secondary memory, which distinguish it from primary memory −

• It is non-volatile, it retains data when power is switched off
• It is large capacities to the tune of terabytes
• It is cheaper as compared to primary memory

HDD (hard disk drive)

A hard drive is a non-volatile storage device with a magnetic disc that stores data permanently. To construct a hard disk, one or more platters are placed in an  air-sealed casing. Data is written onto the platters by moving a magnetic head across them as they rotate. The operating system, installed programs, and the user's files and programs, such as images, music, games, movies, text documents, and so on, are all examples of data that is typically stored on a computer's hard drive.

• A computer's hard disk drive is the primary and usually largest data storage device.

• It can store anywhere from 160 gigabytes to 2 terabytes of data. 

• Hard disk speed is the rate at which data on a hard disk can be read and written.

• A hard disk unit has a fixed rotation speed that ranges from 4500 to 7200 rpm.

• The access time to a disk is measured in milliseconds.

SSD (Solid State Drive)

SSD (Solid State Drive) is another type of non-volatile storage medium used to store and access data. Because it lacks moving components, it has many advantages over HDD, including faster access time, noiseless operation, lower power consumption, and more.

As the price of SSDs has decreased, they have become an excellent replacement for standard hard drives in desktop and laptop computers. It is also appropriate for notebooks and tablets that do not require a large amount of storage.

CD (Compact Disk)

A Compact Disc (CD) is a popular secondary storage device. On its surface, there are tracks and sectors. It has a circular shape and is made of polycarbonate plastic. CDs have a data storage capacity of up to 700 MB. A CD is also known as a CD-ROM (Compact Disc Read-Only Memory), and computers can read the data on a CD-ROM but not write new data to it. We'll need a CD-ROM for this. There are two kinds of CDs-

CDs are classified into two types:

CD-R, or compact disc recordable, - Data written onto it cannot be removed, it can only be read.

CD-RW, or compact disc rewritable, is a type of CD that enables us to delete and rewrite data as many times as we want, so it's also referred to as an erasable CD.

Blu-Ray Disc

Blu-Ray Disc, like DVD, is a high-density optical disc. A Blu-ray disc is required to play PlayStation games and watch High-Definition (HD) movies.

A double-layer Blu-Ray disc has a maximum data storage capacity of 50GB (gigabytes). This is more than 5 times the capacity of a DVD and more than 70 times the capacity of a CD. The format was designed to support high-definition video recording, rewriting, and playback, as well as large-scale data storage; it can actually hold up to 25 Giga Bytes of data or information. If you want to use a Blu-ray disc, you'll need a Blu-ray reader. The name Blu-ray is derived from the technology used to read the disc: 'Blu' is an abbreviation for a blue-violet laser, and 'ray' is an abbreviation for an optical ray.

Pen Drive

Pen drives are small, portable secondary storage devices, also known as flash drives. It connects to a computer via a USB port. It is frequently used to store and transfer data between computers.

The data is stored in a pen drive, which has no moving parts, on an integrated circuit memory chip. An aluminum or plastic case protects this chip. The data storage capacity of a pen drive typically ranges from 2 GB to 128 GB. Furthermore, it is a plug-and-play device, as it does not require any additional hardware or software to operate.

There are so many secondary Memory devices in the world, and we will discuss them in upcoming articles.

 Difference between Primary Memory and Secondary Memory

Primary Memory	Secondary Memory
Primary memory is directly accessible by Processor/CPU	Secondary memory is not directly accessible by the CPU.
Nature of Parts of Primary memory varies, RAM- volatile in nature. ROM- Non-volatile.	It’s always Non-volatile in nature.
Primary memory devices are more expensive than secondary storage devices.	Secondary memory devices are less expensive when compared to primary memory devices.
The memory devices used for primary memory are semiconductor memories.	The secondary memory devices are magnetic and optical memories.
Primary memory is also known as Main memory or Internal memory	Secondary memory is also known as External memory or Auxiliary memory.

So, as we discuss

An area of computer memory that can be accessed directly by the CPU is the primary memory, sometimes referred to as internal memory or internal storage. Secondary memory is persistent, non-volatile computer memory that a processor cannot access directly. Data that can be quickly and easily retrieved, transmitted, and used by applications and services to store data permanently.

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