Minecraft wiki entry for Zero-ticking, associated text: Another method of chaining is to utilize the fact that update chains can be used to manipulate the order in which things are processed in a tick. In the shown example, there are two 0-tick generators. The one on the left has an update chain before powering it, while the one on the right is directly powered. When the input is depowered, the 0-tick generator on the right will activate first as it is directly powered causing its output piston to instantly drop its block. While this is happening, the update chain is retracting. Then, the 0-tick generator on the left will will activate causing its output piston to instantly drop its block.