chip name (a=a, b=b, c=c, d=d, sel[0]=sel[0], sel[1]=sel[1], out=x);
chip name (a=e, b=f, c=g, d=h, sel[0]=sel[0], sel[1]=sel[1]), out=y);
___________________________________________________________^
chip name (a=x, b=y, sel=sel[3], out=out);
}
--Mark