NASM 2.05 based x86 Instruction Reference[ch271]
A.5.247 POR: MMX Bitwise OR POR mm1,mm2/m64 ; 0F EB /r [PENT,MMX] POR xmm1,xmm2/m128 ; 66 0F EB /r [WILLAMETTE,SSE2] POR performs a bitwise OR operation between its two operands (i.e. each bit of the result is 1 if and only if at least one of the corresponding bits of the two inputs was 1), and stores the result in the destination (first) operand.