
i386 and PAE NX


Some newer i386 cpus will contain per-page execute control:  Microsoft Mandated!

Some i386 cpus contain two MMU modes: standard 32bit PTE, or PAE 64-bit PTE

AMD64 architecture contains a specification that bit 63 of the PAE PTE
becomes a NX (non-executeable) bit.

Yes, the NX bit works in 32-bit mode or 64-bit mode (OpenBSD/amd64 uses it).

Intel's unreleased AMD64 clone cpus "Prescott" do NOT support NX 

However, difficult to use.. complex and likely low-performance to support two
MMU modes in the same architecture:

OpenBSD/sparc supports 2 kinds of MMUs: 7000 lines for pmap.c

Typical pmap module is 1300-3000 lines of code

Do not want PAE to be a compile option.

I am trying to convince vendors to make a 32-bit NX extension.

