Hm, while thinking about cellular automatons in hardware, I remembered that some cellular automatons have the left and right cells connected together as well as the top and bottom cells, so that the result is a torus grid. Now, in an asynchronous CA it’s unacceptable to wait for a long signal from one end of the chip to the other. But then an idea came into my mind: If you fold the cells two times, at first in the horizontally in the middle, then vertically in the middle, you get a torus grid if you connect the cells at the edges with the cells above. But you also get four layers. Hm, is that possible with the current chip manufacturing processes?