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<p>level. However, almost all operating systems for the <a href="page.php?w=80386">80386</a> and later x86 processors implement the <a href="page.php?w=flat_memory_model">flat memory model</a>, so they cannot use this capability.  There was no "Executable" flag in the page table entry (page descriptor) in those processors to make this capability available to operating systems using the flat memory model, until AMD added a "no-execute" or NX bit to the page table entry in its <a href="page.php?w=AMD64">AMD64</a> architecture, providing a mechanism</p><p>
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