Choose the slot that matches your CPU's specifications for optimal performance.
Choose the slot that matches your CPU's specifications for optimal performance.
Insert the 8-pin connector and leave the 4-pin section unplugged. Even if your power supply has a different 4-pin or 8-pin option, it's safe to connect that instead; however, the 4-pin isn't required (and is usually not included).
You may also work with it if you possess just an 8-pin version.
What processor are you running? It offers greater performance for the i9-9900K if you're using it at stock settings; I'd recommend connecting both power cables. For an i7, attaching both connectors should have no impact.
Connectors limit how much current they can safely handle before overheating, which could cause damage or fire. The top pins are +12V and the bottom ones are Ground. Each pair of these pins can manage up to 7A or roughly 84W. An 8-pin EPS connector can handle up to 28A or 336W, while a 4-pin one can manage 14A or 168W. If both are connected, the total could reach 42A or 504W—unlikely to occur. The actual limit depends on wire gauge and PSU design. Even at lower loads, cables carry less strain and stay cooler. TL;DR: plugging them in isn't necessary, but it won't harm and keeps cables cooler.