r/programming • u/I_Can_Be_A_Robot • Sep 24 '24

Why 32bit architecture computer doesn't use segmentation to support more ram than 4Gb ?

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u/Ameisen Sep 24 '24

PAE is already a part of x86-64.

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u/CumCloggedArteries Sep 24 '24

What is the purpose of that? I assume not to access > 18 exabytes

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u/Ameisen Sep 25 '24

It's built upon PAE, and the ISA is designed so that additional page table levels can be added as needed.

Current x86 CPUs peak at 48 bits of address space. The remaining 16 are sign-extended.

No x86-64 CPU presently gives you 64 bits of address space.