So, the main result of designing a CPU is a series of masks that essentially indicate where to put what. For example, in this layer, inject boron anywhere the mask doesn't block. The masks aren't wafer sized- they are pretty small, and a machine moves the mask from position to position across the wafer to re-use it. But, at least when I was working on this, some masks would be larger than an individual square (die)- maybe the mask could do 2x2 at a time. In that case, maybe the application of the mask would get you one complete die, and three die off the edge.
