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SMSW -- Store Machine Status Word

Opcode      Instruction     Clocks          Description

0F  01 /4   SMSW r/m16      2/3,pm=2/2      Store machine status word to EA
                                            word

Operation

r/m16 := MSW;

Description

SMSW stores the machine status word (part of CR0) in the two-byte register or memory location indicated by the effective address operand.

Flags Affected

None

Protected Mode Exceptions

#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault

Real Address Mode Exceptions

Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH

Virtual 8086 Mode Exceptions

Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault

Notes

This instruction is provided for compatibility with the 80286; 80386 programs should use MOV ..., CR0.

up: Chapter 17 -- 80386 Instruction Set
prev: SLDT Store Local Descriptor Table Register
next: STC Set Carry Flag