Having no-data symbol in the alphabet is a sure-fire way to have very stable circuitry. I am rusty in the details (I did development a long time ago and not ret

Having no-data symbol in the alphabet is a sure-fire way to have very stable circuitry. I am rusty in the details (I did development a long time ago and not returned for a while), but for O(width) AND-NOTs, two Miller C elements and glitch-free synthesis you can get async logic without metastability issues, just by design. There is a Russian chip named NeuroMatrix: https://en.wikipedia.org/wiki/NeuroMatrix https://en.wikipedia.org/wiki/NeuroMatrix It's main accelerator exploits the idea that deep neural networks need less precision in layers closer to output. So it uses variable-width variable-count multiply-add circuit within single 64x64 multiply-add circuit. At the start there are, say, only two multiplications done, 32x64, but in the last layer you can fire up to 64 multiplications. Was this circuit built with async logic, it will be even faster, because in clocked logic they have to control depth to get to clock frequency for worst case (1x64x64) and can't gain anything except multiplication count for 64x1x1 case. In async setting, the use in the 64x1x1 would be blazingly fast - one bit depth! (I can be wrong here and there - right now I am editing VHDL grammar, adapting it for ANTLR4, sorry; I hope you get the idea, though) I don't know how DeepNorth operates. But I believe they use the same trick or something close to it - it's cheap and impressive.