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Vol. 2A 3-371
INSTRUCTION SET REFERENCE, A-M
FRSTOR—Restore x87 FPU State
ST(7) ← SRC[ST(7)];
FPU Flags Affected
The C0, C1, C2, C3 flags are loaded.
Floating-Point Exceptions
None; however, this operation might unmask an existing exception that has been
detected but not generated, because it was masked. Here, the exception is gener-
ated at the completion of the instruction.
Protected Mode Exceptions
#GP(0) If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.
If the DS, ES, FS, or GS register is used to access memory and it
contains a NULL segment selector.
#SS(0) If a memory operand effective address is outside the SS
segment limit.
#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1.
#PF(fault-code) If a page fault occurs.
#AC(0) If alignment checking is enabled and an unaligned memory
reference is made while the current privilege level is 3.
#UD If the LOCK prefix is used.
Real-Address Mode Exceptions
#GP If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.
#SS If a memory operand effective address is outside the SS
segment limit.
#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1.
#UD If the LOCK prefix is used.
Virtual-8086 Mode Exceptions
#GP(0) If a memory operand effective address is outside the CS, DS,
ES, FS, or GS segment limit.
#SS(0) If a memory operand effective address is outside the SS
segment limit.
#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1.
#PF(fault-code) If a page fault occurs.