3-15
BASIC EXECUTION ENVIRONMENT
32-bit address-size attribute is in force, segment offsets and displacements are 32 bits, allowing
segments of up to 4 GBytes to be addressed.
The default operand-size attribute and/or address-size attribute can be overridden for a particular
instruction by adding an operand-size and/or address-size prefix to an instruction (refer to
Chapter 17, Mixing 16-Bit and 32-Bit Code of the Intel Architecture Software Developers
Manual, Volume 3). The effect of this prefix applies only to the instruction it is attached to.
Table 3-1 shows effective operand size and address size (when executing in protected mode)
depending on the settings of the D/B flag and the operand-size and address-size prefixes.
NOTES:
YYes, this instruction prefix is present.
NNo, this instruction prefix is not present.
Table 3-1. Effective Operand- and Address-Size Attributes
D Flag in Code Segment
Descriptor
00001111
Operand-Size Prefix 66H
NNYYNNYY
Address-Size Prefix 67H
NYNYNYNY
Effective Operand Size
1616323232321616
Effective Address Size
1632163232163216
