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3-324 Vol. 2A FFREE—Free Floating-Point Register
INSTRUCTION SET REFERENCE, A-M
FFREE—Free Floating-Point Register
Description
Sets the tag in the FPU tag register associated with register ST(i) to empty (11B).
The contents of ST(i) and the FPU stack-top pointer (TOP) are not affected.
This instruction’s operation is the same in non-64-bit modes and 64-bit mode.
Operation
TAG(i) ← 11B;
FPU Flags Affected
C0, C1, C2, C3 undefined.
Floating-Point Exceptions
None.
Protected Mode Exceptions
#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1.
#MF If there is a pending x87 FPU exception.
#UD If the LOCK prefix is used.
Real-Address Mode Exceptions
Same exceptions as in protected mode.
Virtual-8086 Mode Exceptions
Same exceptions as in protected mode.
Compatibility Mode Exceptions
Same exceptions as in protected mode.
64-Bit Mode Exceptions
Same exceptions as in protected mode.
Opcode Instruction 64-Bit
Mode
Compat/
Leg Mode
Description
DD C0+i FFREE ST(i) Valid Valid Sets tag for ST(i) to empty.