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INSTRUCTION SET REFERENCE
FXRSTORRestore FP And MMX
State And Streaming SIMD
Extension State (Continued)
Protected Mode Exceptions
#GP(0)
For an illegal memory operand effective address in the CS, DS, ES, FS, or
GS segments, or if an attempt is made to load non-zero values to reserved
bits in the MXCSR field.
#SS(0)
For an illegal address in the SS segment.
#PF (fault-code) For a page fault.
#NM
If CR0.EM = 1.
#NM
If TS bit in CR0 is set.
#AC
For unaligned memory reference. To enable #AC exceptions, three condi-
tions must be true(CR0.AM is set; EFLAGS.AC is set; current CPL is 3).
Real Address Mode Exceptions
Interrupt 13
If any part of the operand would lie outside of the effective address space
from 0 to 0FFFFH.
#NM
If CR0.EM = 1.
#NM
If TS bit in CR0 is set.
Virtual 8086 Mode Exceptions
Same exceptions as in Real Address Mode.
#AC
For unaligned memory reference if the current privilege level is 3.
#PF (fault-code) For a page fault.
Comments
State saved with FXSAVE and restored with FRSTOR, and state saved with FSAVE and restored
with FXRSTOR, will result in incorrect restoration of state in the processor. The address size
prefix will have the usual effect on address calculation, but will have no effect on the format of
the FXRSTOR image.
The use of Repeat (F2H, F3H) and Operand-size (66H) prefixes with FXRSTOR is reserved.
Different processor implementations may handle these prefixes differently. Usage of these
prefixes with FXRSTOR risks incompatibility with future processors.
