NASM 2.05 based x86 Instruction Reference[ch205]
A.5.182 MOVUPD: Move Unaligned Packed Double-Precision FP Values MOVUPD xmm1,xmm2/mem128 ; 66 0F 10 /r [WILLAMETTE,SSE2] MOVUPD xmm1/mem128,xmm2 ; 66 0F 11 /r [WILLAMETTE,SSE2] MOVUPD moves a double quadword containing 2 packed double-precision FP values from the source operand to the destination. This instruction makes no assumptions about alignment of memory operands. To move data in and out of memory locations that are known to be on 16- byte boundaries, use the MOVAPD instruction (section A.5.157).