How MMU and Cache Work Together ?

1. MMU Translates Virtual Address → Physical Address

   • Every memory access from the CPU (in virtual address space) goes through the MMU.

   • It uses page tables to resolve Virtual Address (VA) → Physical Address (PA).

2. MMU Provides Memory Attributes

   • In addition to translation, the MMU tells the CPU:

     • Is this region cacheable?

     • Should it be write-back, write-through, or non-cacheable?

     • Is it device memory or normal memory?

3. Cache Uses MMU Info to Decide Behavior

• If a region is cacheable, cache stores/fetches data for that region.

• If non-cacheable, all accesses go directly to RAM (or MMIO).

• MMU attributes control whether cache is used at all.

Example Flow (ARM Cortex-A CPU):

Load [VA = 0xFFFF0000]
   ↓
MMU:
   - Translates to PA = 0x10000000
   - Checks page tables → memory type = normal, inner-cacheable, write-back
   ↓
Cache:
   - Checks if PA = 0x10000000 is in L1/L2
   - If hit → return cached data
   - If miss → fetch from RAM, store in cache











This is why bootloaders and OS kernels carefully configure MMU 
and cache together.