Memory is a storage holder. It stores the data or information temporarily or permanently. We think that memory is a physical device that is used for storing but we have another type of memory which is called virtual memory. Let us explore what is the key difference between cache memory and virtual memory.
Difference between Cache Memory and Virtual Memory in tabular form
| Cache Memory | Virtual Memory |
| Cache memory is the high-speed memory that contains recently accessed data of the main memory | Virtual memory is the logical type of memory that increases the capacity of the main memory |
| It increases the accessing speed of the CPU | It increases the degree of multiprogramming |
| It can also be called a storage unit | It is not defined as a storage unit. Rather, can also be called a technique |
| The size of cache memory is small as compared to the virtual memory | The size of virtual memory is large as compared to the cache memory |
| Hardware completely manages the cache memory | The operating system manages the virtual memory |
| Cache memory is fast as compared to the virtual memory | Virtual memory is not as fast the cache memory |
| There is no need for mapping structures in a cache memory | Virtual memory requires mapping structure to map the physical address and the logical address |
| Cache memory can usually be SRAM (Static RAM) | As it is virtually present, Windows operating system support the virtual memory and provides space for it |
What is Cache Memory?
We know that there are various types of memories and there is always a tilt of confusion that which memory refers to what.
Let us go into detail about what means to us by cache memory.
Cache memory is the storage device, but again we need to know what kind of data it stores. It carries the data or copies of the files which are been recently accessed by the processor or the CPU. We know that CPU registers are the fastest in speed.
Cache memory is slower than the CPU registers but faster than virtual memory. The rate of data transfer from the cache memory to the processor is quite fast. Cache memory is efficient as it is smaller in size, faster in speed, it is located near the core of the processor that consists of the copies of data that is frequently used by the CPU locations.
Cache memory can be called the buffer between the main memory and the CPU as it holds the data and gives quick access to the required files. Let us understand some terms here.
Cache memory contains blocks inside it and these blocks are called cache lines. When the information required by the processor is available in the cache memory then it is called a cache hit. When there is the unavailability of the required data/information in the cache memory then it is called a cache miss. In this case, the data is called from the main memory.
Cache memory organization is divided into two types. One is a single-level organization that contains a single cache. Other is the multi-level organization which contains three types of caches. Level1 (L1), Level2 (L2), Level3 (L3) cache. L1 is the smallest cache having the fastest data transferring rate. It the most frequently used.
A cache is faster computer memory compared to virtual memory and main memory but is slightly costly as it has high accessing speed.
Let us discuss virtual memory.
What is Virtual Memory?
As its name suggests, it is not a physical memory device as a hard disk. Instead, it is something that provides storage virtually without acquiring physical space. Virtual memory is a technique that performs the execution of heavy programs which are not completely placed in the main memory. Users can execute the larger programs easily.
As we have discussed above the working of cache memory, now let us also understand the working of virtual memory.
Virtual memory address consists of several pages. Also, the main memory carries different pages. We know that the virtual memory has larger space as compared to the main memory. So memory mapping comes into existence here. Memory mapping is used to map the physical and logical address to the main memory.
The pages of virtual memory are mapped with the pages of the main memory and if the pages of main memory are filled, the previously filled page gets transferred to the hard disk and the place for the new page is evacuated. This is how the process works. Virtual memory pages can be linked with the main memory pages, i.e. two memory addresses can share with one main memory page.
Virtual memory enhances the degree of multiprogramming and CPU utilization. Windows operating systems support the use of virtual memory.
We have all the points that are important to know when learning the concept of cache memory and virtual memory.
Author
Shraddha Changune
SVKM’s Institute of Technology, Dhule
