There is only cable. Unless the pulleys are stuck due to friction, the tension is equal in all sections of the cable. The load is being lifted by six segments of the cable, so 6x the tension: the machine's advantage is 6x.
Even so - it's "just" a compound pulley system. The advantage of White's pulley seems to be the reduction of friction by only having two axles, and synchronized rope movement so that the rope doesn't need to slip over the sheaves.
