FFREE — Free Floating-Point Register

Opcode	Instruction	64-Bit Mode	Compat/Leg Mode	Description
DD C0+i	FFREE ST(i)	Valid	Valid	Sets tag for ST(i) to empty.

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.