Why are page sizes in operating systems always powers of 2?

Answer 1

Answer: Recall that paging is implemented by breaking up an address into a page and offset number. It is most efficient to break the address into X page bits and Y offset bits, rather than perform arithmetic on the address to calculate the page number and offset. Because each bit position represents a power of 2, splitting an address between bits results in a page size that is a power of 2.

Answer 2

Recall that paging is implemented by breaking up an address into a page and offset number. It is most efficient to break the address into X page bits and Y offset bits, rather than perform arithmetic on the address to calculate the page number and offset. Because each bit position represents a Page_size_are_always_power_of_2of 2, splitting an address between bits results in a page size that is a power of 2.

Answer 3

The page table size is in powers of two because the virtual to linear address translation hardware uses part of the virtual address (the high order part) to select an entry in the page descriptor table, and it uses the rest of the virtual address (the low order par) to select an offset within the physical page selected by that page table entry. Looking at the low order part, any address range that goes from zero to some number of all-one bits is a power of two in size.