User Guide

8 Overview of the AMD64 Architecture
AMD64 Technology 24592—Rev. 3.15—November 2009
Legacy mode is compatible with existing 32-bit processor implementations of the x86 architecture.
Processors that implement the AMD64 architecture boot in legacy real mode, just like processors that
implement the legacy x86 architecture.
Throughout this document, references to legacy mode refer to all three submodes—protected mode,
virtual-8086 mode, and real mode. If a function is specific to either of these submodes, then the name
of the specific submode is used instead of the name legacy mode.