The curious interaction between PAE and NX

Carmen Crincoli covered the interaction between PAE and NX on his own blog, so I'll merely incorporate his remarks by reference.

(And notice again the concession to backwards compatibility. Without the backwards compatibility work, XP SP2 would have shipped with NX support and an asterisk, "* and those of you who have device drivers that are not PAE-ready will not be able to take advantage of these new security enhancements. We could've done something to make your systems secure, but we decided not to do it in order to teach you a lesson.")

Comments (5)
  1. PaulJ says:


  2. Yeah, I’m a guy. Don’t get too hung up on the name, I’m Italian, not Hispanic. :)

  3. DrPizza says:

    What I’ve never figured out is why Intel didn’t use the extra PTE space back when they introduced it with the PPro (it was the PPro, wasn’t it? I can’t remember now).

    The need for read-but-not-execute has been plainly obvious since the frigging Morris worm, if not before. As such we can somewhat understand why the 386 has no 3-bit protection (it had to work on small machines and no-one really expected buffer overflows to be so significant), but by the time the PAE came along there was no such excuse. PAE gave us enough room in the PTEs for an NX bit, but Intel didn’t bother.

  4. Carmen: If someone asks, you can aim them at your only (that I know of) famous male namesake.

  5. DrPizza says:

    Why does the index page claim five comments but only 4 appear?

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