� When using a 32-bit register to address memory in the real mode, contents of the register must never exceed 0000FFFFH. � In the protected mode, any value can be used in a 32-bit register that is used to indirectly address memory. � as long as it does not access a location outside the segment, dictated by the access rights byte � In the 64-bit mode, segment registers are not used in modern portfolio theory and investment analysis 7th edition pdf a 'real mode' program uses BIOS subroutines along with OS subroutines whereas a 'protected mode' program uses only OS subroutines. instruction code differs since opcodes for registers are different and offset addresses are of different length.
And using 32-bit registers in protected mode (32-bit protected mode) will cut down the size of the code generally. Improved addressing modes - In real mode, programs can only form addresses with constant values, the BX or BP register, and the SI or DI register.