image/svg+xmlEMMS—Empty MMX Technology StateInstruction Operand EncodingDescription Sets the values of all the tags in the x87 FPU tag word to empty (all 1s). This operation marks the x87 FPU data registers (which are aliased to the MMX technology registers) as available for use by x87 FPU floating-point instruc-tions. (See Figure 8-7 in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1, for the format of the x87 FPU tag word.) All other MMX instructions (other than the EMMS instruction) set all the tags in x87 FPU tag word to valid (all 0s).The EMMS instruction must be used to clear the MMX technology state at the end of all MMX technology procedures or subroutines and before calling other procedures or subroutines that may execute x87 floating-point instructions. If a floating-point instruction loads one of the registers in the x87 FPU data register stack before the x87 FPU tag word has been reset by the EMMS instruction, an x87 floating-point register stack overflow can occur that will result in an x87 floating-point exception or incorrect result.EMMS operation is the same in non-64-bit modes and 64-bit mode.Operationx87FPUTagWord := FFFFH;Intel C/C++ Compiler Intrinsic Equivalentvoid _mm_empty()Flags AffectedNoneProtected Mode Exceptions#UDIf CR0.EM[bit 2] = 1.#NMIf CR0.TS[bit 3] = 1.#MFIf there is a pending FPU exception.#UD If the LOCK prefix is used.Real-Address Mode Exceptions Same exceptions as in protected mode.Virtual-8086 Mode ExceptionsSame exceptions as in protected mode.Compatibility Mode ExceptionsSame exceptions as in protected mode.64-Bit Mode ExceptionsSame exceptions as in protected mode.OpcodeInstructionOp/ En64-Bit ModeCompat/Leg ModeDescriptionNP 0F 77EMMSZOValidValidSet the x87 FPU tag word to empty.Op/EnOperand 1Operand 2Operand 3Operand 4ZONANANANA

This UNOFFICIAL reference was generated from the official Intel® 64 and IA-32 Architectures Software Developer’s Manual by a dumb script. There is no guarantee that some parts aren't mangled or broken and is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.