Cache memory is a small, high-speed storage area in a computer. It stores copies of the data from frequently used main memory locations. There are various independent caches in a CPU, which store instructions and data.
- The most important use of cache memory is that it is used to reduce the average time to access data from the main memory.
- The concept of cache works because there exists locality of reference (the same items or nearby items are more likely to be accessed next) in processes.
By storing this information closer to the CPU, cache memory helps speed up the overall processing time. Cache memory is much faster than the main memory (RAM). When the CPU needs data, it first checks the cache. If the data is there, the CPU can access it quickly. If not, it must fetch the data from the slower main memory.
Types of Cache Memory
- 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.
- 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.
- 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.
Cache Hit and 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
Point to Know:
- 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).
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.