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To bridge the processor memory performance gap, hardware designers are increasingly relying on memory at the top of the memory hierarchy to close / reduce the performance gap. Next is cache memory followed by conventional DRAM memory, followed by disk storage with different levels of performance including SSD, optical and magnetic disk drives. At the very top, the highest performing storage is CPU registers which are the fastest to read and write to. Memory hierarchy is arranging different kinds of storage present on a computing device based on speed of access. Let us see the memory levels in terms of size, access time, bandwidth. They are used to store removable files and are the cheapest and largest in size (1-20 TB). Tertiary storage devices like magnetic tape are present at level 4. They are cheaper than main memory and larger in size generally in a few TB. Secondary storage devices like Magnetic Disk are present at level 3. This memory is implemented by using dynamic RAM. Main memory is less expensive than cache memory and larger in size generally in Gigabytes. It directly communicates with the CPU and with auxiliary memory devices through an I/O processor. It is expensive and smaller in size generally in Megabytes and is implemented by using static RAM. They are implemented by using Flip-Flops.Ĭache memory is used to store the segments of a program that are frequently accessed by the processor. Registers are most expensive and smallest in size generally in kilobytes. As they are present inside the CPU, they have least access time. The registers are present inside the CPU. Here the devices are arranged in a manner Fast to slow, that is form register to Tertiary memory. In Memory Hierarchy the cost of memory, capacity is inversely proportional to speed. Level 4: Optical disks or magnetic types or tertiary Memory Level 3: Magnetic disks or secondary memory

It separates the computer storage based on hierarchy.

The Computer memory hierarchy looks like a pyramid structure which is used to describe the differences among memory types.