NASM 2.05 based x86 Instruction Reference[ch253]
A.5.229 PINSRW: Insert Word PINSRW mm,r16/r32/m16,imm8 ;0F C4 /r ib [KATMAI,MMX] PINSRW xmm,r16/r32/m16,imm8 ;66 0F C4 /r ib [WILLAMETTE,SSE2] PINSRW loads a word from a 16-bit register (or the low half of a 32- bit register), or from memory, and loads it to the word position in the destination register, pointed at by the count operand (third operand). If the destination is an MMX register, the low two bits of the count byte are used, if it is an XMM register the low 3 bits are used. The insertion is done in such a way that the other words from the destination register are left untouched.