If you take it to an extreme the flaw is apparent. Let's say "bogomips" is the name of a real world accurate benchmark.
If a CPU at full performance gives 100 bogomips at 2 watts and idles at 1 watt by your metric the score is 50.
On the other hand, if a CPU at full performance gives 200 bogomips at 2 watts and idles at a small fraction under 2 watts, your metric also gives a score of ~50.
It's obvious the 200 bogomips processor is way more efficient than the 100 bogomips processor. Something is missing.
I think both idle watts and TDP are somewhat irrelevant. Maybe it should be bogomips / actual watt draw (different from nominal TDP) at full speed. Assuming you can keep the processor busy. Not being able to keep the processor busy doesn't really reflect on processing efficiency. Except that it is better for the wasted watts to be as low as possible.
A true efficiency, like a true benchmark is elusive, because what is "normal use"? Somewhere between "no work, all waste" and "full use, maximum efficiency".
The 13900KS boosts to 6ghz at 320w.
The 13900K boosts to 5.8ghz at 253w.
That’s a 3.4% increase in clock speed at the cost of a 26.5% increase in power. The marginal power cost for the frequency increase is way out of line.
"but the extra 'S' in the name denotes that this is premium-binned silicon that hits 6 GHz on two cores — 200 MHz faster than the 12900K"These new Intels are desktop CPUs. They also have Performance and Efficiency cores. Ideally, they'd prioritize using E-cores, and only as many as needed to complete tasks within an acceptable period. In effect, though, they're not very smart, and you've got to get into overclocking and undervolting to get them into a state that resembles AMD's TDP-limited ECO Mode that provides 80% of the performance at 50% of the power.
For example, let's contrast the 13700k to the ancient 7920X. The 13700K benchmarks to 47106, with a TDP of 250, a performance per watt of 188. Compare that to a 7920X, which benchmarks to half that at 23607, with a TDP of 140W, a performance per watt that's less than 170. The 13700K is clearly an improvement if we stopped there!
Except we don't, because the wasted watts matter a lot: the 13700K needs 125W just to power its cores, whereas the 7920X needs 55W. Adjusting our performance per watt to performance per watt per wasted watt, we get 1.57 for the 13700K, but 3 for the 7920X. That old CPU is twice as good at turning energy into work.
The 13700K is unquestionably a higher performing CPU than the 7920X, but it's very hard to, with a straight face, call it an improvement based on energy consumption =)