A practical version of Lee's multicast switch architecture

To close, let's estimate the overall chip count required to add the multicast capability to a point-to-point network with 256 inputs and outputs. We will assume that for the chips that have little internal memory, we are constrained only by pin count, that each chip has 128 pins available for inputs and outputs and that the data paths are one bit wide. For the example con guration then, 32 chips are required for the concentrator, 16 for the adder, 6 for the dacs and 56 for the copy network. Assuming that each of the 64 btcs consists of one memory chip and one control chip, we have 128 more chips for the btcs. This gives a total of 238 chips or less than one per port. The fifos following the btcs would add perhaps another chip each. Hence, the cost of adding a multicast capability to Lee's architecture is about two chips per port.