> A fundamental problem is that the attack surface is so, so huge. Even if their security researchers are doing blue-sky research on both very small and very broad areas of processor functionality, they're going to miss a lot.

Sure. If they had patched a bunch of Spectre vulnerabilities and independent researchers had discovered a few more that would be one thing, but as far as I can tell they have patched _zero_ while independent researches have found many and it has been years since the initial attack. Many of these follow very similar patterns and "in what cases is protected data exposed via speculative execution" is something that an architect or engineer could definitely assess.

Generally all these workarounds have a measurable slowdown associated with them. This mitigation apparently has an up to 50% cost. It's unlikely many of them have been silently fixed without people noticing.