Minecraft wiki entry for Clock, associated text: Efficiency: An efficient approach to making long-period clocks is to start with a repeater loop of 9 to 16 repeaters (up to 64 ticks), then add multiplier banks with N of 7, 5, and 3 (bigger is more efficient). Doublings should be done with T flipflops, as 2 of those are cheaper and perhaps shorter than a 4-multiplier. A couple of notes: