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Date:      Fri, 30 Nov 2012 18:58:06 +0400
From:      Ilya Kazakevich <>
To:        Thomas Mueller <>
Subject:   Re: i386 vs amd64
Message-ID:  <>
In-Reply-To: <>
References:  <>

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> How does the system know what is OS and what is 32-bit apps?
"OS" works in kernel space while application is not.

PAE affects paging system allowing software to address 2^36 bytes of memory.
You can access it in kernel space, but user space applications are limited
to 2^32 bytes of virtual memory (even less than 2^32 because of mappings).

If you are interested in memory management in IA-32 (and IA-32e) here are
good links:
1) official guide:
2) nice (human-readable) book:

> Where would GCC fit in this regard, or Clang for that matter?
If you write app for user-space (not kernel module) you should not care
about PAE.
You simply compile it as you would do it for system with out of PAE.


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