I know the circuit well I did several of them Many years ago... The "Clock is the rate at which the data moves through those logic IC's. They weren't static. Your '285 takes 2 4 bit binary words and "Adds them together... although it is a parallel process it Still was "Clocked Logic"... There is a specific rate at which the data moves through the adder... That is the clock rate. TTL was also famous for it's quiescent current and when you produce a chip of that complexity there's a lot of gates drawing power... They get even hotter when you run them fast... BTW LS means "Low Power Schottky" which was about as fast as "regular" 7400 series logic and drew about 1/10th the power and there were ECL logic chips that could ruin your whole day... If you touched them... kind of a circle because ECL and things like USB are Very similar in theory/technology as ECL was the fore runner of what is called LVDS or "Low Voltage Differential Signalling". The theory is that it doesn't take as much power (heat) to move a pair of wires about a common LOW center voltage as it does to take one conductor and slam it between Vcc and ground as fast as you can as for one.. the parasitic capacitance's aren't as big so it doesn't take as much energy (heat) to charge and discharge them. Does this help?
Doc