ARM Technical Support Knowledge Articles

Why is the MMU implemented in 2 levels? What is the need for a DTE and PTE in the MMU implementation?

Applies to: Mali-200

Answer

The Mali MMU needs to represent a 4GB virtual address space as it handles a 32 bit address space
(2^32 = 4GB).


The page directory (DTE) is used to split the representation of that 4GB space into 1024 sections.

The page directory then store pointers to the second level page tables representing each of those
4MB (4GB/1024) sections.

Each page table (PTE) the further divides that 4MB section into 1024 smaller blocks, each 4kB large,
called a page.

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