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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><HTML><HEAD><TITLE>80386 Programmer's Reference Manual -- Opcode LMSW</TITLE></HEAD><BODY><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="LLDT.htm"> LLDT Load Local Descriptor Table Register</A><BR><B>next:</B><A HREF="LOCK.htm"> LOCK Assert LOCK# Signal Prefix</A><P><HR><P><H1>LMSW -- Load Machine Status Word</H1><PRE>Opcode Instruction Clocks Description0F 01 /6 LMSW r/m16 10/13 Load r/m16 in machine status word</PRE><H2>Operation</H2><PRE>MSW := r/m16; (* 16 bits is stored in the machine status word *)</PRE><H2>Description</H2>LMSW loads the machine status word (part of CR0) from the sourceoperand. This instruction can be used to switch to Protected Mode; if so,it must be followed by an intrasegment jump to flush the instructionqueue. LMSW will not switch back to Real Address Mode.<P>LMSW is used only in operating system software. It is not used inapplication programs.<H2>Flags Affected</H2>None<H2>Protected Mode Exceptions</H2>#GP(0) if the current privilege level is not 0; #GP(0) for an illegalmemory operand effective address in the CS, DS, ES, FS, or GSsegments; #SS(0) for an illegal address in the SS segment; #PF(fault-code)for a page fault<H2>Real Address Mode Exceptions</H2>Interrupt 13 if any part of the operand would lie outside of the effectiveaddress space from 0 to 0FFFFH<H2>Virtual 8086 Mode Exceptions</H2>Same exceptions as in Real Address Mode; #PF(fault-code) for a pagefault<H2>Notes</H2>The operand-size attribute has no effect on this instruction. Thisinstruction is provided for compatibility with the 80286; 80386 programsshould use <A HREF="MOVRS.htm">MOV</A> CR0, ... instead.<P><HR><P><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="LLDT.htm"> LLDT Load Local Descriptor Table Register</A><BR><B>next:</B><A HREF="LOCK.htm"> LOCK Assert LOCK# Signal Prefix</A></BODY>?? 快捷鍵說(shuō)明
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