At least you hope, it is more power efficient due to advanced manufacturing process. And then a totally disappointment: new CPU consumes significantly more both under load and idle. The AI-extensions are also missing. ECC is missing in all 8300G/8500G/8600G/8700G.
Got a link for the ECC claim? Last I read, the ECC issues with the AM5 platform were mostly fixed (at least many vendors are claiming ECC compatibility again, which they didn't a year ago).
5xxxG are also known for missing official support, only PRO favors have it.
Since ECC is for robustness I'd really prefer when both AMD and ASUS/ASRock/Gigabyte/MSI/... mention ECC support in the specification. Last time I've checked, only ASUS did mention it for consumer AM5 mainboards. (Gigabyte did it for (at least) one simple but expensive server mainboard.) While for AM4 it wasn't such an issue for other manufacturers too.
Yes, the 5700g and 5600g can score lower amount of peak power, but you need to compare the power used against a metric like time to calculate efficiency.
The $179 8500G is competing with the $449 Ryzen 7 7800X3D in efficiency. It's a blood bath.
