"Jack Andrews" <effbiae@xxxxxxxxx> writes: > for (i=0; i < n; i += W) { > asm("movq %0 %%mm1\n\t" > "paddq %%mm1 %%mm0" You are missing commas between the operands. movq %0, %%mm1 Instead of using inline assembler I recommend that you use the functions in mmintrin.h. Ian