A.5.206 PAVGUSB: Average of unsigned packed 8-bit values
PAVGUSB mm1,mm2/m64 ; 0F 0F /r BF [PENT,3DNOW]
PAVGUSB adds the unsigned data elements of the source operand to the
unsigned data elements of the destination register, then adds 1 to the
temporary results. The results of the add are then each independently
right-shifted by one bit position. The high order bits of each element
are filled with the carry bits of the corresponding sum.
This instruction performs exactly the same operations as the PAVGB MMX
instruction (section A.5.205).