EMMS
Usage: EMMS Modifies flags: None
Used to clear the MMX state before using registers for FPU operations.
Empty MMX State
EMMS ; 0F 77 [PENT,MMX]
EMMS sets the FPU tag word (marking which floating-point registers are available) to all ones, meaning all registers are available for the FPU to use. It should be used after executing MMX instructions and before executing any subsequent floating-point operations.
All other MMX instructions (other than the EMMS instruction) set all the tags in x87 FPU tag word to valid, all zeros. 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.
EXAMPLE:
emms