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    SubjectRe: PAE and PSE ??
    Rafael J. Wysocki wrote:
    >
    > Well, "AMD64 Architecture Programmer’s Manual" says the following:
    >
    > The choice of 2 Mbyte or 4 Mbyte as the large physical-page size
    > depends on the value of CR4.PSE and CR4.PAE, as follows:
    > - If physical-address extensions are enabled (CR4.PAE=1), the
    > large physical-page size is 2 Mbytes, regardless of the value
    > of CR4.PSE.
    > - If physical-address extensions are disabled (CR4.PAE=0)
    > and CR4.PSE=1, the large physical-page size is 4 Mbytes.
    > - If both CR4.PAE=0 and CR4.PSE=0, the only available page
    > size is 4 Kbytes.
    >

    That would be a retroactive redef on the part of AMD; it probably makes
    sense for x86-64 if someone thinks that is may drop support for 4 MB
    pages at some point in the distant future. Still, I'm not sure Intel
    would agree with the definition as stated, although I haven't looked in
    the docs.

    This is all extremely theoretical, since there has never been a chip
    with PAE=1 and PSE=0, and I wouldn't expect one to appear any time soon.

    -hpa
    -
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