Explain the concept of cache line size in CPU design.

Cache line size refers to the amount of data that can be stored in a single cache line within the CPU's cache memory. It determines the granularity at which data is fetched from main memory into the cache. When the CPU needs to access data, it checks if it is present in the cache. If the data is not found, a cache miss occurs, and the CPU fetches a cache line from main memory into the cache.

The cache line size is important because it affects the efficiency of memory access. If the cache line size is too small, the CPU may need to fetch multiple cache lines to retrieve a larger chunk of data, resulting in more cache misses and slower performance. On the other hand, if the cache line size is too large, it may lead to wasted space in the cache and inefficient memory utilization.

Cache line size is typically determined by the CPU's architecture and can vary between different processors. It is often chosen to align with the memory bus width or the size of data blocks commonly accessed by the CPU. Optimizing the cache line size is crucial for improving the overall performance and reducing memory latency in CPU design.