Overclocked threadrippers can hit 500W[1]. I can see peltiers and 'vapochill' style phase-change cooling making a comeback...
1. https://www.anandtech.com/show/13124/the-amd-threadripper-29...
1. https://www.anandtech.com/show/13124/the-amd-threadripper-29...
But there are an awful lot of mobile processors with passive cooling or complex heat pipes, and it would take more convincing that such a scheme would also fail there.
I'm also wondering if it might be useful for 'race to idle' situations by extending the time until thermal throttling kicks in.
I can't imagine why anyone would be more inclined to use a peltier as wattage increases. Higher wattages make that idea progressively worse unless you have some very specific and strange requirements.
The worst spots aren't much worse than the median spots (over calculating silicon, not cache). Anything big enough to be a hot spot, like a big ALU, is big enough to represent a large portion of your power budget. The main goal is to get all the heat away from the chip, and putting peltiers on a large portion of the chip gives you more heat to take away. For anything significantly smaller than that, the heat bleeds out without the need of a peltier. There might be a middle ground where peltiers could make a real life difference, but I'm skeptical.
> or it could mean circuits with far more layers than we can manage now
That sounds like you're cooling the entire chip, which is the worst time to use a peltier.