What would you mean by incoherence, though?

There's a plenty of possible cellular automations that are neither quantum mechanical nor relativistic, and it's not too hard to construct one that would approximate classical mechanics at macroscopic scale, but wouldn't in any way resemble quantum mechanics as we know it at microscale*, nor would be relativistic.

• caveat: you could represent classical behaviour within quantum mechanical framework, it's just that you wouldn't want to.