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According to Microsoft, the page file sizes of 64-bit and 32-bit Windows are 256TB and 16TB respectively.

In 64-bit, the virtual address looks like this:

64-bit virtual address format

With 4 levels of 9-bit memory mapping fields and 12-bit offset within page, 64-bit Windows can map maximum 29+9+9+9+12 byte = 256TB.

In 32-bit, the virtual address looks like this:

32-bit virtual address format

With 2 levels of 10-bit memory mapping fields and 12-bit offset within page, 32-bit Windows should be able to map maximum 210+10+12 byte = 4GB? Then why 16TB?

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  • Does this answer your question? Increasing page file size on 32 bit WinXP
    – helper
    Apr 5, 2020 at 12:41
  • Is it mean that the extra 15.99609375 TB maximum page file size under 32-bit Windows comes from the external storage device (such as HDD)? Then why there s no such "buffer" for 64-bit Windows? Thanks. Apr 5, 2020 at 13:28

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Your arithmetic is correct : 2 power 32 gives 4 GB.

However, a file's size is counted in blocks.

If the size of one block is 4 K, which is standard for NTFS, you would have a maximal size in bytes of:

4 GB x 4 K = 16 TB

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    @Didier - We are not a discussion forum. If you want to ask the author something, ping the author, otherwise, it will be unclear who you are asking a question to. Furthermore, lengthy discussions, shouldn't happen in the comment section.
    – Ramhound
    Apr 5, 2020 at 17:03
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Have you considered PAE in your equation?

It says here that adding the /PAE (or /pae) argument in the boot.ini file allows for bigger pagefiles in 32-bit Windows, up to 16TB.

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    Welcome on the SU! The question already asks for, why 16TB is the max. Answering that how can this maximum increased to 16TB is not an answer to the question (on the top).
    – peterh
    Apr 5, 2020 at 18:30

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