Desing a Direct Mapping

Question

Design a direct mapping structure with 128KB cache and 128 MB memory size. Write the address limits of main memory, line numbers of cache, block numbers and number of tag bits. Explain each structure and write the advantages and drawbacks

Answer 1

I designed a direct-mapped cache with 128 KB size for a main memory of 128 MB. Each block is 4 bytes, giving 32,768 cache lines and 33,554,432 memory blocks. Memory addresses are 27 bits, divided into a 10-bit tag, 15-bit cache line index, and 2-bit block offset. This structure allows each memory block to map to exactly one cache line, making lookups simple and fast. The main advantage is low hardware complexity and high access speed, while the drawback is that conflicts can occur if multiple memory blocks map to the same line, potentially reducing cache efficiency.