NASM 2.05 based x86 Instruction Reference[ch282]
A.5.258 PSUBx: Subtract Packed Integers PSUBB mm1,mm2/m64 ; 0F F8 /r [PENT,MMX] PSUBW mm1,mm2/m64 ; 0F F9 /r [PENT,MMX] PSUBD mm1,mm2/m64 ; 0F FA /r [PENT,MMX] PSUBQ mm1,mm2/m64 ; 0F FB /r [WILLAMETTE,SSE2] PSUBB xmm1,xmm2/m128 ; 66 0F F8 /r [WILLAMETTE,SSE2] PSUBW xmm1,xmm2/m128 ; 66 0F F9 /r [WILLAMETTE,SSE2] PSUBD xmm1,xmm2/m128 ; 66 0F FA /r [WILLAMETTE,SSE2] PSUBQ xmm1,xmm2/m128 ; 66 0F FB /r [WILLAMETTE,SSE2] PSUBx subtracts packed integers in the source operand from those in the destination operand. It doesn't differentiate between signed and unsigned integers, and doesn't set any of the flags. - PSUBB operates on byte sized elements. - PSUBW operates on word sized elements. - PSUBD operates on doubleword sized elements. - PSUBQ operates on quadword sized elements.