NASM 2.05 based x86 Instruction Reference[ch023]
A.5.4 ADDPD: ADD Packed Double-Precision FP Values ADDPD xmm1,xmm2/mem128 ; 66 0F 58 /r [WILLAMETTE,SSE2] ADDPD performs addition on each of two packed double-precision FP value pairs. dst[0-63] := dst[0-63] + src[0-63], dst[64-127] := dst[64-127] + src[64-127]. The destination is an XMM register. The source operand can be either an XMM register or a 128-bit memory location.