I don't see how the cost of supporting outmoded instructions would be significant. The decoder is a tiny proportion of the die, and not a bottleneck at all. Obs

I don't see how the cost of supporting outmoded instructions would be significant. The decoder is a tiny proportion of the die, and not a bottleneck at all. Obsolete instructions that can't be translated to the same uops everything else uses are already microcoded anyway. I'd bet the instruction set difference is mainly level of SIMD support. Sunny Cove will have AVX2, Tremont won't have enough execution units to go wider than SSE2.