WP has an adequate discussion of paging, which I think I understand.. However I am confused by the articles repeated use of the term Page Frame.

I thought frames and pages were different things. Could someone please clarify the difference.


Short version: "page" means "virtual page" (i.e. a chunk of virtual address space) and "page frame" means "physical page" (i.e. a chunk of physical memory).

That's it, pretty much. It's important to keep the two concepts distinct because at any given time, a page may not be backed by a page frame (it could be a zero-fill page which hasn't been accessed, or paged out to secondary memory), and a page frame may back multiple pages (sometimes in different address spaces, e.g. shared memory or memory-mapped files).

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    $\begingroup$ Also multiple virtual address pages may be mapped to the same physical page frame (often with Copy On Write) and in a NUMA system a single virtual address page may map to multiple physical page frames (to exploit locality). $\endgroup$ – Paul A. Clayton Apr 30 '13 at 12:06
  • $\begingroup$ I think I covered the first point you made, but the second point is also well-made. Distributed-memory architectures complicate things a lot. $\endgroup$ – Pseudonym May 3 '13 at 5:10
  • $\begingroup$ Yes, reading comprehension failure! :-( $\endgroup$ – Paul A. Clayton May 3 '13 at 11:55
  • $\begingroup$ Could you answer the followings? What does "be backed by" mean? What should be understood? $\endgroup$ – itsnotmyrealname Apr 15 at 10:42

Physical memory is organized into frames and virtual memory into pages. The "page frame" term is a bit confusing and in my opinion wikipedia shouldn't use it. What they really mean by "page frame" is a block/group/segment of physical memory, which is equivalent to a frame. So they should instead use the term "frame", not "page frame".

In short remember:

  • page = block of consecutive virtual memory
  • frame = block of consecutive physical memory

That is how i use it.


A page frame is a storage unit within the main memory, while a page is the contents in the frame.


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