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What is cache memory?


Cache Memory is also known as SRAM (Static RAM). And I assume you the full form of RAM.
So, why cache memory is used in Computer?

Hmm, Nice question.
As we know data is transferred from secondary memory to primary memory for making change in the file. And from primary memory it goes to the CPU via Bus for execution.
CPU is so fast that the data transfer RAM become slow for the CPU. As result CPU remain idle most of the time.
So, to optimize the usage of the CPU, cache memory was introduced.
Cache memory is hardware memory which store the instructions that are executed frequently by the system.
To understand the concept of cache memory?
Let’s take an example:

 Suppose, CPU is at Point A, Cache memory is at point B and RAM is at point C.
So, who will require more time to reach to CPU?
Point B or C?
Obviously, B(Cache) because its closure to CPU.
It will require less time to transfer data to the CPU.Because it is nearer to CPU.
When a process is executed CPU check whether the instruction are stored in  the cache memory or not if yes then it executed direct through cache memory as result time get saved.


The basic operation of a cache memory is as follows:
  • When the CPU needs to access memory, the cache is examined. If the word is found in the cache, it is read from the fast memory.
  • If the word addressed by the CPU is not found in the cache, the main memory is accessed to read the word.
  • A block of words one just accessed is then transferred from main memory to cache memory. The block size may vary from one word (the one just accessed) to about 16 words adjacent to the one just accessed.
  • The performance of the cache memory is frequently measured in terms of a quantity called hit ratio.
  • When the CPU refers to memory and finds the word in cache, it is said to produce a hit.
  • If the word is not found in the cache, it is in main memory and it counts as a miss.
  • The ratio of the number of hits divided by the total CPU references to memory (hits plus misses) is the hit ratio.




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