Intel 64 and IA-32 Architectures Software Developers Manual Volume 2A, Instruction Set Reference, A-M

3-322 Vol. 2
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.
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.