A.5.176 MOVQ: Move Quadword to/from MMX Register
MOVQ mm1,mm2/m64 ; 0F 6F /r [PENT,MMX]
MOVQ mm1/m64,mm2 ; 0F 7F /r [PENT,MMX]
MOVQ xmm1,xmm2/m64 ; F3 0F 7E /r [WILLAMETTE,SSE2]
MOVQ xmm1/m64,xmm2 ; 66 0F D6 /r [WILLAMETTE,SSE2]
MOVQ copies 64 bits from its source (second) operand into its
destination (first) operand. When the source is an XMM register, the
low quadword is moved. When the destination is an XMM register, the
destination is the low quadword, and the high quadword is cleared.