The widest bus a truth table will be made for. A truth table lists an output for every combination of its inputs, so it is for narrow combinational logic - mostly single-bit, with the occasional multiplexer - and a table of a wide bus is not something anyone can read. The algebraic evaluator behind it accordingly works in `uint32` and stops here, where the fast simulator carries any width. Making that a stated limit, refused at the door with a message, is better than a second evaluator quietly claiming to do what the first does: the two would have to be held to each other over the whole range, and the wide half of that range is the half nobody uses.