A.5.260 PSUBSIW: MMX Packed Subtract with Saturation to Implied Destination
PSUBSIW mm1,mm2/m64 ; 0F 55 /r [CYRIX,MMX]
PSUBSIW, specific to the Cyrix extensions to the MMX instruction set,
performs the same function as PSUBSW, except that the result is not
placed in the register specified by the first operand, but instead in
the implied destination register, specified as for PADDSIW (section
A.5.200).