A.5.78 FEMMS: Faster Enter/Exit of the MMX or floating-point state
FEMMS ; 0F 0E [PENT,3DNOW]
FEMMS can be used in place of the EMMS instruction on processors which
support the 3DNow! instruction set. Following execution of FEMMS, the
state of the MMX/FP registers is undefined, and this allows a faster
context switch between FP and MMX instructions. The FEMMS instruction
can also be used _before_ executing MMX instructions.