Memory Hierarchy

The computer memory can be divided into 5 major hierarchies that are based on use as well as speed. A processor can easily move from any one level to some other on the basis of its requirements. These five hierarchies in a system’s memory are register, cache memory, main memory, magnetic disc, and magnetic tape.

In this article, we will take a look at the Memory Hierarchy according to the GATE Syllabus for CSE (Computer Science Engineering). Read ahead to learn more.

Table of Contents

What is Memory Hierarchy?
Frequently Asked Questions

What is Memory Hierarchy?

The memory unit refers to an essential type of component in a digital computer. And it is required for storing various programs and data. The memory can be typically classified into two separate categories:

1. Main Memory- It refers to the memory unit that helps in establishing direct communication with a system’s CPU. This main memory is also often referred to as Random Access Memory or RAM.

2. Auxiliary Memory- It refers to the memory units that help us in providing backup storage. For example, magnetic tapes and magnetic disks are the most popularly used auxiliary memories.

Now, apart from the primary classifications of any unit of memory, the memory hierarchy consists of all of the storage devices that are available in a computer system, ranging from the slow and yet high-capacity auxiliary memory to comparatively faster main memory.

The image given below illustrates the components involved in a typical memory hierarchy.

Auxiliary Memory

The auxiliary memory is basically the highest-capacity, slowest-access, and lowest-cost storage in a given computer system. The auxiliary memory provides us with storage for various data and programs that we want to store for longer or when it’s not in immediate use. Magnetic disks and magnetic tapes are the most popular examples of auxiliary memories.

The magnetic disk refers to a digital computer memory that makes use of a magnetization process in order to write data, rewrite it and also access it. For instance, zip disks, hard drives, and floppy disks provide auxiliary storage.

The magnetic tape refers to a storage medium that would allow users to archive data, collect it, and back it up for different kinds of information.

Main Memory

We also call the main memory of a computer system as RAM or Random Access Memory. This unit of memory directly communicates with the CPU and the auxiliary memory devices. It does it through an I/O processor. Those programs that aren’t required currently in the main memory are ultimately transferred into auxiliary memory in order to provide space for programs and data used currently.

I/O Processor

Managing the transfer of data between the auxiliary and the main memory is the primary function of any I/O Processor.

Cache Memory

The contents or data of the main memory that the CPU uses frequently are stored in the cache memory. It is done so that the system’s processor can access that data easily in a shorter time. Now, whenever the CPU requires memory accessing, it checks the required data first into the cache memory. If the information is found in the system’s cache memory, it is read from the fast memory; else, the CPU would move onto the main memory in order to find the required data.

Frequently Asked Questions on Memory Hierarchy

What is memory and its hierarchy?

The computer memory refers to a storage space in which the computer stores the instructions that are needed for processing, and it can be divided into 5 major hierarchies that are based on use as well as speed. A processor can easily move from any one level to some other on the basis of its requirements. These five hierarchies in a system’s memory are register, cache memory, main memory, magnetic disc, and magnetic tape.

What is memory hierarchy? Why do we need it?

The hierarchy memory unit refers to an essential type of component in a digital computer, and it is required for storing various programs and data. It is applied to get a larger memory space at a low cost. Fast memory has comparatively low storage capacity, and yet it needs a power supply for storing the data, and thus it is costly. The memories that have less cost have a higher access time.

What are the characteristics of memory hierarchy?

The following characteristics are required for Memory Hierarchy Design:

Capacity
Access Time
Performance
Cost per Bit

What is memory mapping?

Memory-mapping refers to the mechanism that maps a file’s portion, an entire file, or on disk to an address range within the address space of an application. This application can thus access files on a disk the same way in which it accesses dynamic memory.

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