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Chapter 14 -- 80386 Real-Address Mode
prev: 14.3 Interrupt and Exception Handling
next: 14.5 Switching Back to Real-Address Mode
14.4 Entering and Leaving Real-Address Mode
Real-address mode is in effect after a signal on the RESET pin. Even if the
system is going to be used in protected mode, the start-up program will
execute in real-address mode temporarily while initializing for protected
mode.
14.4.1 Switching to Protected Mode
The only way to leave real-address mode is to switch to protected mode. The
processor enters protected mode when a
MOV to CR0 instruction sets the PE
(protection enable) bit in CR0. (For compatibility with the 80286, the LMSW
instruction may also be used to set the PE bit.)
Refer to
Chapter 10
"Initialization" for other aspects of switching to
protected mode.
up:
Chapter 14 -- 80386 Real-Address Mode
prev: 14.3 Interrupt and Exception Handling
next: 14.5 Switching Back to Real-Address Mode