There would be a single clock typically but OP is right in the sense that as the signal propagates through the system you can get nondeterministic effects: http

There would be a single clock typically but OP is right in the sense that as the signal propagates through the system you can get nondeterministic effects: https://en.wikipedia.org/wiki/Metastability_(electronics) https://en.wikipedia.org/wiki/Metastability_(electronics) In practice the probability of that is just driven low enough that it's not an issue.