Correct, I was responding to parent writing "At what point does the complexity of CPU architectures become so difficult to reason about that we just accept the

Correct, I was responding to parent writing "At what point does the complexity of CPU architectures become so difficult to reason about that we just accept the performance penalty of keeping it simpler?" I think we may be seeing an industry-wide shift away from SMT because the performance penalty is small and the complexity cost is high, if so that fits parent's speculation about the trend. In a narrow sense Zenbleed isn't related to SMT but OP's question seems perfectly relevant to me. I come from a security background and on average more complicated == less secure because engineering resources are finite and it's just harder and more work to make complicated things correct.