The ATX PWR 6 Pin is supplemental power to the pci lanes of the motherboard. If you are using only one GPU, you do not need to install it.

The supplemental power is only needed when running more than two PCI devices at one time.

The 6 pin atx is the same cable that you would use for a PCI 6+2 pin, and just leave the +2 hidden.

There is zero benefit from running the extra 6 pin with a single pci device because you are only pulling less than 75w from the pci lane. The extra 6 pin was added to alleviate power draw on the pci lanes when 3 and 4 GPU’s were used and pulling 225-300 watts would actually melt the 24 pin power cable. The 6 pin would provide the necessary voltage instead of relying on the 24pin cable, which would keep the 24 pin from melting. It wasn’t for stability of the GPU.

Lots of people will swear it helps, but it isn’t providing any extra power or stability if the pci lanes aren’t populated. The power spikes that happen typically occur on the 8, 12, or 12+4 pins because they have a much higher ability to request much more power.

I do always plug my 6pin in, because I like it being installed if I over do any intense overclocking, but if you are not doing extreme overclocking with at least two GPU’s, it isn’t going to pull enough power to matter much. Plugging in the 6 pin will not hurt anything, so plug it in if you like the aesthetic, and don’t if you don’t want to.