Memory Management Unit (MMU)

The MMU examines all memory references on the memory bus, translating these requests (Virtual Memory) into physical addresses in main memory.

Why are MMUs needed when you have DMAs?

They both serve different functions.

MMU (Memory Management Unit) handles virtual memory management, address translation, memory protection, and caching.

DMA (Direct Memory Access) is focused on efficient data transfer between memory and peripherals, bypassing the CPU.

When you do data → data transfers from memory, is the MMU used?

Yes, but at the end of the day, its still the cpu that executes a ld instruction and st instruction. The MMU is always involved on every memory access because it maps virtual address to physical address.