Hello friends, in this article you will be getting to know regarding memory hierarchy in computer architecture classified according to Access time, Speed, Size, Cost. The memory hierarchy is one of the most important topics to learn as a computer student. Every computer student should have a brief knowledge regarding this topic, so I recommend everyone to spend some 5 minutes and understand regarding this topic.

In computer architecture, we divide memory into different levels according to speed and size. Memory Hierarchy can be said as different levels of memory in common conversations. Since, everyone nowadays uses computers either their desktop, laptop, or mobile computers which makes it is important for everyone to know how memory is processed, classified, and used in our computer architecture. The memory hierarchy is one of the most important in every competitive exam. There are 4 types of memory or storage in the architecture of our general-purpose computers, which include the following.

One of the major differences in memory hierarchy is in terms of size. As shown in the chart from top to bottom, the size is increasing. The top one contains the least amount of data and the number of data increases as we move towards the base leading to the huge size difference between the different hierarchies of memory. In our system, nowadays we have all levels of memory in the computer balancing cost and performance. Registers hold the least amount of data. The sizes of registers contain 8  bytes, 16 bytes, or 32 bytes. Registers are also of different types containing general-purpose register, address register, MBR, etc. They are directly associated with the CPU. After registers come to Cache Memory. They come in kilobytes (KB) or megabytes(MB). Although Main Memory (RAM) is another level of memory we can even call Cache Memory as SRAM and Main memory as DRAM. The sizes of Main Memory include in GB i.e. 8 GB, 16 GB, etc. Then comes USB/ Flash Memory. They are the most popular these days. The reason, being faster read and write speed. They also come in GB and also sometimes in TB also. After which comes Magnetic/ Hard Disks. They come on TB. And finally comes, Magnetic Tapes/ Tape drives, they are at the bottom of the Hierarchy pyramid reason, again being the highest in size. They come on PB or EB.

While talking about the cost, many people think that since Tertiary Storage has the most amount of capacity, they are the most costly. But, it is the complete opposite. Reason being, access time. We will come back in access time in a little bit but all the reason for the cost of storage devices is mainly time. The more the access time the more the price. So, the cost of Magnetic Tapes/ Tape drives is the least and registers are the highest. Following up, the cost increases as we go towards the peak of the pyramid of the memory hierarchy.

In the memory hierarchy, there is the concept of time is money. If we access data from registers, it will be the fastest and then cache memory and then main memory and following up to magnetic tapes/ tape drives. If we talk about the size it follows the top to down increase and if we talk about access time and speed it follows the bottom to top increase. On average, magnetic tapes take 100 milliseconds to access the data, following up to 10 millisecond by magnetic disk/ hard disk, 10 microseconds by flash memory, 100 nanoseconds by Main memory, 10 nanoseconds by cache memory, and then comes the fastest to date registers which have an average speed of 1 nanosecond.

If we talk about the frequency or the use cases, the register has the highest frequency and magnetic tape/ tape drives have the lowest frequency. The register is accessed mainly as it is associated with the CPU, then comes cache memory, then main memory, after which USB/ Flash memory, then after Magnetic Disk/ Hard Disk and at the end Magnetic Tapes/ Tape drives. Since Magnetic tapes/ tape drives are mainly used as backups, their frequency is very low but we use registers with every input-output operation, its frequency is highest.

So, this is all about the memory hierarchy in computer architecture. Hope you understood about the topic. If you have any doubt please leave a comment down below.