This seems to have its own issues and the proof is in the final cores.

ARM’s entire gross profits are about half of AMD’s R&D budget, but ARM cores have soundly beat x86 in IPC for years now (since around A78) and the most recent generations seem to be beating them in total performance, perf/watt, and core size.

We now have all three of the big ARM-based cores (Apple, ARM, and Qualcomm) beating x86. Apple you could maybe write off as unlimited money, but all three isn’t just coincidence.

If that weren’t enough, ARM designers are releasing new cores every year instead of every other year meaning they are doing around twice as many layout and validations despite the massively lower budget.

Before I get the “ARM only makes cores” excuses, I’d note that ARM announced that they’ve been working on their own server chips and that work is obviously having to fit within their same (comparatively tiny) budget.

It seems fairly obvious. Spring legacy garbage drives up complexity and cost (eg, ARM reduced A-series decoder size by 75% when they dropped 32-bit mode which was still way less complex than x86). This complexity drives up development time and cost. It also drives up validation cost and time.

There’s also a physical cost. Large, high frequency uop caches and cache controllers are better than just decoders on x86, but worse than not needing them at all is better still. Likewise, you hear crazy stuff like the x86 overly-strict memory model not mattering because you can speculate it away. That speculation means more complexity, more power, and more area.

Once you’re done with enough of these work-around, you get a chip that is technically as fast, but it cost more to design, costs more to validate, costs more to fab, costs more to buy, costs more to operate, and carries an opportunity cost from taking so much longer to get to market.