Unlike the 8086 and 80286, 32-bit effective addresses can be generated (via the address-size prefix); however, the value of a 32-bit address may not exceed 65535 without causing an exception. For full compatibility with 80286 real-address mode, pseudo-protection faults (interrupt 12 or 13 with no error code) occur if an effective address is generated outside the range 0 through 65535.
up:
Chapter 14 -- 80386 Real-Address ModeFigure 14-1. Real-Address Mode Address Formation
19 3 0
+---------------------------------+---------+
BASE | 16-BIT SEGMENT SELECTOR | 0 0 0 0 |
+---------------------------------+---------+
+
19 15 0
+---------+---------------------------------+
OFFSET | 0 0 0 0 | 16-BIT EFFECTIVE ADDRESS |
+---------+---------------------------------+
=
20 0
LINEAR +---------------------------------------------+
ADDRESS | X X X X X X X X X X X X X X X X X X X X X X |
+---------------------------------------------+
prev: Chapter 14 -- 80386 Real-Address Mode
next: 14.2 Registers and Instructions