It is a specific kind of architecture that is patented. If they implement a different kind, they can patent and use it. The problem with patenting something very general is that someone will always find a way to do it another way. Of course except cases like patenting pi. Then, still we would probably say that we invented a new number called as phi, obtain it via Taylor expansion and use it to compute the area of a circle by dividing the diameters square to the inverse of this number. Until we obtain a patent in this way, the other company may dominate the market because it found it first. But that is the idea of the patent.