What is the role of memory controllers and how are they different from the MMU inside the processor? is it that the MMU job is to translate virtual addresses to physical ones (among other things) and send this physical address to the memory controller that sends specific signals to the DRAM and return the result to the MMU? or is the memory controller part of the MMU?
An MMU traditionally would be responsible for handling virtual memory and cache. The memory controller would handle the physical signalling involved in communicating to external memory. Typically the MMU is tightly coupled to the processor core while the memory controller is a peripheral on an internal bus.