Cache memory in computer organization is a speedier and smaller chunk of memory with access times that are as close as registers. Cache memory has a shorter access time than primary memory in a memory hierarchy. Because cache memory is typically relatively little, it basically acts as a buffer. The data or contents of the main memory that are frequently accessed by the CPU are stored in the cache memory so that the processor may access them quickly. The CPU first checks the cache memory whenever it needs to access memory. If the data is not there in cache memory, the CPU switches to main memory. Cache memory is a type of memory that sits between the CPU and the main memory.
Need of cache memory in Computer Organization:
Although data in primary memory can be accessible faster than data in secondary memory, primary memory access times are typically in the few microseconds range, whereas the CPU can conduct operations in the nanosecond range. The system’s performance suffers as a result of the time lag between accessing data and acting on it, and the CPU has to sit idle for long periods of time. To reduce the time gap, a new memory segment called cache memory comes into play.
Basic Operations of a Cache Memory :
When the CPU needs to access memory, it looks into the cache. The word is read from the fast memory if it is found in the cache.
If the word sought by the CPU is not there in the cache, the word is in main memory.
After that, a block of words accessed recently is transferred from main memory to cache memory. The size of the block can range from one word (the one you just accessed) to approximately 16 words adjacent to the one you just visited.
The hit ratio is a metric that is useful to assess cache memory performance.
The CPU makes a hit when it refers to memory and finds the word in cache.
If the word is not in the cache, it’s in main memory, and then it is a miss.
The number of hits divided by the total number of CPU memory references (hits plus misses) is the hit ratio.
Types of Cache Memory in Computer Organization :
Level 1 Cache – It refers to the processor’s initial level of cache memory. It’s present in a modest amount in each of the processor’s cores individually.
Level 2 Cache – It’s the second cache memory level, which is there in both inside and outside the CPU.
Level 3 Cache – It is the CPU’s third level of cache memory, which is external to the CPU and shared by all of its cores.