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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