Cache Memory in Computer Architecture

Cache Memory-

 

  • Cache memory is a Random Access Memory.
  • The main advantage of cache memory is its very fast speed.
  • It can be accessed by the CPU at much faster speed than main memory.

 

Location-

 

  • Cache memory lies on the path between the CPU and the main memory.
  • It facilitates the transfer of data between the processor and the main memory at the speed which matches to the speed of the processor.

 

 

  • Data is transferred in the form of words between the cache memory and the CPU.
  • Data is transferred in the form of blocks or pages between the cache memory and the main memory.

 

Purpose-

 

  • The fast speed of the cache memory makes it extremely useful.
  • It is used for bridging the speed mismatch between the fastest CPU and the main memory.
  • It does not let the CPU performance suffer due to the slower speed of the main memory.

 

Execution Of Program-

 

  • Whenever any program has to be executed, it is first loaded in the main memory.
  • The portion of the program that is mostly probably going to be executed in the near future is kept in the cache memory.
  • This allows CPU to access the most probable portion at a faster speed.

 

Step-01:

 

Whenever CPU requires any word of memory, it is first searched in the CPU registers.

Now, there are two cases possible-

 

Case-01:

 

  • If the required word is found in the CPU registers, it is read from there.

 

Case-02:

 

  • If the required word is not found in the CPU registers, Step-02 is followed.

 

Step-02:

 

  • When the required word is not found in the CPU registers, it is searched in the cache memory.
  • Tag directory of the cache memory is used to search whether the required word is present in the cache memory or not.

 

Now, there are two cases possible-

 

Case-01:

 

  • If the required word is found in the cache memory, the word is delivered to the CPU.
  • This is known as Cache hit.

 

Case-02:

 

  • If the required word is not found in the cache memory, Step-03 is followed.
  • This is known as Cache miss.

 

Step-03:

 

  • When the required word is not found in the cache memory, it is searched in the main memory.
  • Page Table is used to determine whether the required page is present in the main memory or not.

 

Now, there are two cases possible-

 

Case-01:

 

If the page containing the required word is found in the main memory,

  • The page is mapped from the main memory to the cache memory.
  • This mapping is performed using cache mapping techniques.
  • Then, the required word is delivered to the CPU.

 

Case-02:

 

If the page containing the required word is not found in the main memory,

  • A page fault occurs.
  • The page containing the required word is mapped from the secondary memory to the main memory.
  • Then, the page is mapped from the main memory to the cache memory.
  • Then, the required word is delivered to the CPU.

 

Multilevel Cache Organization-

 

  • A multilevel cache organization is an organization where cache memories of different sizes are organized at multiple levels to increase the processing speed to a greater extent.
  • The smaller the size of cache, the faster its speed.
  • The smallest size cache memory is placed closest to the CPU.
  • This helps to achieve better performance in terms of speed.

 

Example-

 

Three level cache organization consists of three cache memories of different size organized at three different levels as shown below-

 

Size (L1 Cache) < Size (L2 Cache) < Size (L3 Cache) < Size (Main Memory)

 

 

To gain better understanding about Cache Memory,

Watch this Video Lecture

 

Next Article- Cache Mapping Techniques

 

Get more notes and other study material of Computer Organization and Architecture.

Watch video lectures by visiting our YouTube channel LearnVidFun.

Summary
Cache Memory in Computer Architecture
Article Name
Cache Memory in Computer Architecture
Description
Cache memory in computer architecture is a special memory that matches the processor speed. Cache memory is located on the path between the processor and the memory. Its fast speed makes it extremely useful.
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Gate Vidyalay
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