Cache Memory

Cache memory is a special type of high-speed memory located close to the CPU in a computer. It stores frequently used data and instructions, So that the CPU can access them quickly, improving the overall speed and efficiency of the computer.

It is a faster and smaller segment of memory whose access time is as close as registers. In a hierarchy of memory, cache memory has access time lesser than primary memory. Generally, cache memory is used as a buffer.

In this article we will see cache memory in detail.

What is Cache Memory?

Data in primary memory can be accessed faster than secondary memory but still, access times of primary memory are generally in a few microseconds, whereas the CPU is capable of performing operations in nanoseconds. Due to the time lag between accessing data and acting on data performance of the system decreases as the CPU is not utilized properly, it may remain idle for some time. In order to minimize this time gap new segment of memory is Introduced known as Cache Memory.

It is based on principle of locality of reference, which refers to the observation that program tries to access a relatively small portion of their address space at any given time, and repeatedly tries to access some portion of the memory. For ex: In fees department of your college, transactions are accessed frequently to check on the dues.

Key Features of Cache Memory

1. Speed: Faster than the main memory (RAM), which helps the CPU retrieve data more quickly.
2. Proximity: Located very close to the CPU, often on the CPU chip itself, reducing data access time.
3. Function: Temporarily holds data and instructions that the CPU is likely to use again soon, minimizing the need to access the slower main memory.

Role of Cache Memory

The role of cache memory is explained below,

• Cache memory plays a crucial role in computer systems.
• It provide faster access.
• It acts buffer between CPU and main memory(RAM).
• Primary role of it is to reduce average time taken to access data, thereby improving overall system performance.

Benefits of Cache Memory

Various benefits of the cache memory are,

1. Faster access: Faster than main memory. It resides closer to CPU , typically on same chip or in close proximity. Cache stores subset of data and instruction.
2. Reducing memory latency: Memory access latency refers to time taken for processes to retrieve data from memory. Caches are designed to exploit principle of locality.
3. Lowering bus traffic: Accessing data from main memory involves transferring it over system bus. Bus is shared resource and excessive traffic can lead to congestion and slower data transfers. By utilizing cache memory , processor can reduce frequency of accessing main memory resulting in less bus traffic and improves system efficiency.
4. Increasing effective CPU utilization: Cache memory allows CPU to operate at a higher effective speed. CPU can spend more time executing instruction rather than waiting for memory access. This leads to better utilization of CPU’s processing capabilities and higher overall system performance.
5. Enhancing system scalability: Cache memory helps improve system scalability by reducing impact of memory latency on overall system performance.

Working of Cache Memory

In order to understand the working of cache we must understand few points:

• Cache memory is faster, they can be accessed very fast
• Cache memory is smaller, a large amount of data cannot be stored

Whenever CPU needs any data it searches for corresponding data in the cache (fast process) if data is found, it processes the data according to instructions, however, if data is not found in the cache CPU search for that data in primary memory(slower process) and loads it into the cache. This ensures frequently accessed data are always found in the cache and hence minimizes the time required to access the data.

How does Cache Memory Improve CPU Performance?

Cache memory improves CPU performance by reducing the time it takes for the CPU to access data. By storing frequently accessed data closer to the CPU, it minimizes the need for the CPU to fetch data from the slower main memory.

What is a Cache Hit and a Cache Miss?

Cache Hit: When the CPU finds the required data in the cache memory, allowing for quick access.On searching in the cache if data is found, a cache hit has occurred.

Cache Miss: When the required data is not found in the cache, forcing the CPU to retrieve it from the slower main memory.On searching in the cache if data is not found, a cache miss has occurred

Performance of cache is measured by the number of cache hits to the number of searches. This parameter of measuring performance is known as the Hit Ratio.

Hit ratio=(Number of cache hits)/(Number of searches)

Types of Cache Memory

1. L1 or Level 1 Cache: It is the first level of cache memory that is present inside the processor. It is present in a small amount inside every core of the processor separately. The size of this memory ranges from 2KB to 64 KB.
2. L2 or Level 2 Cache: It is the second level of cache memory that may present inside or outside the CPU. If not present inside the core, It can be shared between two cores depending upon the architecture and is connected to a processor with the high-speed bus. The size of memory ranges from 256 KB to 512 KB.
3. L3 or Level 3 Cache: It is the third level of cache memory that is present outside the CPU and is shared by all the cores of the CPU. Some high processors may have this cache. This cache is used to increase the performance of the L2 and L1 cache. The size of this memory ranges from 1 MB to 8MB.

Difference Between Cache and RAM

Although Cache and RAM both are used to increase the performance of the system there exists a lot of differences in which they operate to increase the efficiency of the system. 

Conclusion

In conclusion, cache memory plays an important role in enhancing the speed and efficiency of computer systems. By storing frequently accessed data and instructions close to the CPU, cache memory minimizes the time required for the CPU to access information, thereby reducing latency and improving overall system performance.