My PSU is an 850w EVGA supernova, it comes with 2x PCI power cables both are 8pin from the PSU and terminates as 8 pin (6+2) and 6 pin on each cable, the Graphics card I am looking at getting (RX 7800XT) needs 2x8pin, can I just connect 2 x PCI power cables to the PSU and use the 8pin (6+2) on each cable (leaving the 6 pin on both unused). Alternatively can I just get a new PSU cable that is 8pin from the PSU with 2 x 8pin on the other end to connect to the Graphics card?
It’s all on the 12v rail so it shouldn’t matter, should it?
When a card needs two connectors you should always use two separate cables for each. The pigtails are when you use two cards.
So for the past 9 years I’ve been using the 8pin (from PSU) to 8pin + 6pin (to graphics card) this was wrong?
No it’s not wrong to use a single cable, it’s just not ideal. Depending on the quality of the cable and the connectors it may help a bit. 2 cables will always have lower resistance than a single one.