RAM And ROM in Computer Systems:-
Let's first know about what is RAM and how it works:-
Definition of RAM:-
It stands for Random Access Memory(RAM).It is also known as read/write memory that allows CPU to read as well as write data and instructions into it.
RAM is used for the temporary storage of input data, output data and intermediate result.
RAM (Random Access Memory) is the hardware in a computer device where the operating system (OS),
application programs and data in current use are kept so they can be quickly reached by the device's processor.
RAM is the main memory in a computer. It is much faster to read from and write to than other kinds of storage,
such as a hard disk drive (HDD), solid-state drive (SSD) or optical drive.
Random Access Memory is volatile memory which means that when the power is turned off, the content of this memory are lost forever. That means data is retained in RAM as long as the computer is on, but it is lost when the computer is turned off. When the computer is rebooted, the OS and other files are reloaded into RAM, usually from an HDD or SSD.
Functions of RAM:-
Because of its volatility, RAM can't store permanent data. RAM can be compared to a person's short-term memory, and a hard disk drive to a person's long-term memory. Short-term memory is focused on immediate work, but it can only keep a limited number of facts in view at any one time. When a person's short-term memory fills up, it can be refreshed with facts stored in the brain's long-term memory.
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| Random access memory |
There are two categories of RAM as follows:-
1.Dynamic RAM(DRAM):- It is made up of memory cells where each cell is composed of one capacitor and one transistor. DRAM must be refreshed continually to store information. DRAM is slower, less-expensive and occupies less space on the computer's motherboard.
DRAM is a type of RAM that stores each bit of data on a separate capacitor.
This is an efficient way to store data in memory, because it requires less physical space to store the same amount of data than if it was stored statically.
A DRAM chip can hold more data than an SRAM (static RAM) chip of the same size can.
However, the capacitors in DRAM need to constantly be refreshed to keep their charge, so DRAM requires more power than SRAM.
Still, because DRAM can hold more data than SRAM and because it is significantly less expensive to manufacture,
DRAM is the most common type of memory found in personal computer systems. While there are many types of DRAM available, the most common type is synchronous DRAM SDRAM, which is a faster version of standard DRAM. This is the type of memory most computers use for their main system memory.
2.Static RAM(SRAM):-It retains the data as long as power is provided to the memory chip.
SRAM needs not be refreshed periodically. It uses multiple transistors for each memory cell.It does not use capacitor. SRAM is often used cache memory due to its high speed .
SRAM is more expensive and faster than DRAM.
Function of RAM:-
lets understand how it works in a computer systems:-
How Does The RAM work?
Random Access Memory(RAM) also known as any memory address,
can be accessed directly. Originally, the term Random Access Memory was used to distinguish regular core memory from offline memory.
Offline memory typically referred to magnetic tape from which a specific piece of data could only be accessed by locating the address sequentially, starting at the beginning of the tape. RAM is organized and controlled in a way that enables data to be stored and retrieved directly to and from specific locations.
Other types of storage -- such as the Hard Drive and CD-ROM- are also accessed directly or randomly, but the RAM access isn't used to describe these other types of storage.
RAM is similar in concept to a set of boxes in which each box can hold a 0 or a 1. Each box has a unique address that is found by counting across the columns and down the rows. A set of RAM boxes is called an array, and each box is known as a cell. To find a specific cell, the RAM controller sends the column and row address down a thin electrical line fetched into the chip. Each row and column in a RAM array has its own address line. Any data that's read flows back on a separate data line.
RAM is physically small and stored in microchips. It's also small in terms of the amount of data it can hold. A typical laptop computer may come with 8 gigabytes of RAM, while a hard disk can hold 10 terabytes. Most PCs enable users to add RAM modules up to a certain limit. Having more RAM in a computer cuts down on the number of times the processor must read data from the hard disk, an operation that takes longer than reading data from RAM.
RAM access time is in nanoseconds, while storage memory access time is in milliseconds.
How much RAM do you need in your Computer System:-
The amount of RAM needed all depends on what the user is performing task in a computer system. When the user is performing video editing, image editing, gaming, It's recommended that a
system have at least 8 GB RAM, though more is desirable.
have at least 3GB of RAM to run Photoshop CC on a Mac. However, if the user is working with other applications at the same time, even 8GB of RAM can slow things down.
Definition of ROM:-
It stands for Read Only Memory(ROM).It is also known as non-volatile memory or permanent storage. It does not lose the contents when the power is turned OFF.
ROM can have data and instructions written to it only one time. Once a ROM chip is programmed at the time of manufacturing it cannot be reprogrammed or rewrite. So, it has only read capability, not write.
ROM is a read-only memory, it cannot be changed;
It is permanent and non-volatile memory, it also holds its content even when power is turned off.
By contrast, random access memory (RAM) is volatile; it is lost when power is turned off.
The use of the similar term “non-volatile memory” is applicable here (more on that later.)
One could say that ROM is, in a sense, “stateful” in its enduring state, where RAM is “stateless.”
In a typical modern computer, there are numerous ROM chips located on the motherboard and a few on expansion boards. The chips are essential for the basic input/output system (BIOS), boot up, reading and writing to peripheral devices, basic data management and the software for basic processes for certain utilities.
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There are three categories of ROM as follows:-
- Programmable ROM(PROM):-It is also non-volatile memory in nature. Once a PROM has been programmed, it's content can never be changed. It is one-time programmable device.
These types of memories are found in Video game consoles, mobile 📱 phones, implantable medical devices and high definition multimedia interfaces.
2.Erasable Programmable ROM(EPROM):-It is similar to PROM ,but it can be erased by exposure to strong ultraviolet light 🔦 then rewritten. So it is also known as Ultraviolet Erasable Programmable ROM(UVEPROM).
3.Electrically Erasable Programmable ROM(EEPROM):-It is similar to EPROM ,but it can be erased electrically, the rewritten electrically and the burning process is reversible by exposure to electric pulses. It is the most flexible type of ROM ,and is now commonly used for holding BIOS.
Apart from above memory, there is also some other memory that helps to primary memory which are as follows:-
- Cache Memory:-It is a storage buffer that stores the data which is used most often temporarily and makes them available to CPU at a fast rate. Cache Memory is a very high-speed memory placed in between RAM and CPU. It increases the speed of processing.
Cache Memory is very expensive ,so it is smaller in size. Generally Computers have cache memory of sizes 256toKB to 2MB.
- Flash Memory:-It is a kind of semiconductor based non-volatile rewritable memory. It is used in digital camera, mobile phone and printer etc.
- Virtual Memory:-It is a technique that allows the execution of processes that are not completely in main memory. One major advantage of this scheme is that programs can be larger than main memory.
1 Comments
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