Looking at the Cinebench R15 results it seems like the M1 x86 actually had better perf/Watt than the 5800U despite the oversite the M1 is running this 2013 benchmark via emulation.

Note: If you hit the expandos you'll see nearly every 5800U result is coming from a 30W/25W TDP 5800U. Even if you take the most favorable R15 test (multicore), the 25W value for the 5800U, and a 15W value for the M1 (despite the page saying 10W) that still comes out with perf/watt in favor of the M1 emulating the benchmark. If you look at the first native release of Cinebench (R23 in 2020) you'll see the reality that the M1 runs at about the exact same speed (slightly ahead in single core, slightly behind in multicore) at 1/2 the Wattage.

For comparison an entire Mac Mini system pulls 30W from the wall when running a compute benchmark workload https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste... including conversion loss, peripherals, memory, and anything else.

Interesting thank you! Also the primary/secondary core of the M1 is pretty clever. Intel 13th gen uses a similar strategy now, but not AMD yet, which is surprising considering their chiplet approach.

I think the new 7950x3d is primary/secondary also.

Not exactly. One chiplet has more L3 cache, but the other one can run at higher clock speeds, so which one to prefer depends on the application. Which makes it a horrible mess from a software/OS perspective.