Minecraft wiki entry for Logic, associated text: Design C has a speed of 2 ticks if output is 1, but 1 tick if the output is 0. Similarly, the other designs take 1 tick if the output is 0, but are immediate (and not isolated) if the output is 1. If the player must synchronize (or isolate) the output, consider placing a 1-tick repeater in front of the "fast" input (input A for C, input B for the others).