generated at
CPUの補助電源8+4PINはLN2のようなOCしない限り8PINだけつければいい
from 自作PC build（2022）

基本いらないらしい
>@Yacamochi_db: 最近のCPU用コネクタって「8 + 4」だったり「8 + 8」だったりするけど、i9 9900Kを5 GHzにオーバークロックして動画エンコードするくらいなら「8」だけで全然余裕だから、4本足りないからって気にする必要は（ほぼ）ない。
>
>@Yacamochi_db: @from_AviciHell 実際に試してないので何ともですが、5.3 GHz以上に行くなら必要かも。オーバークロック競技向けですね～w
https://superuser.com/questions/1379482/do-i-need-both-the-8-pin-and-4-pin-cpu-power-plug-for-my-msi-b450-pro-carbon
2018年の回答
> From experience, it suffices to install the 8 pin connector on the left.
> The right 4-pin-connector is basically a redundancy that the CPU may draw upon under extreme load most likely only relevant when you do extreme overclocking.
> (The board manufacturers most likely also build in some more extra room in case the next CPU generation needs more power.)
> So only connect the 2 ports (CPU_PWR_1) on the left, and leave the right one (CPU_PWR_2) empty. If your system won't boot or doesn't run stable, only then you should consider buying the extra cable or upgrading your PSU.
https://www.bestbuy.com/site/questions/msi-mpg-z490-gaming-edge-wifi-socket-lga1200-usb-c-gen1-intel-motherboard-with-led-lighting/6412362/question/c7920985-ae1f-3333-b322-0bf3a3ce7f74
>The 4 pin is only necessary if you are doing extreme overclocking, such as LN2. Otherwise the 8 pin will provide all the power you will need.