Minecraft wiki entry for Memory, associated text: The JK flip-flop's complement function (when J and K are 1) is only meaningful with edge-triggered JK flip-flops, as it is an instantaneous trigger condition. With level-triggered flip-flops (e.g. design C), maintaining the clock signal at 1 for too long causes a race condition on the output. Although this race condition is not fast enough to cause the torches to burn out, it makes the complement function unreliable for level-triggered flip-flops.