https://www.techpowerup.com/293410/galax-rtx-3090-ti-hof-first-graphics-card-with-dual-16-pin-connectors-1200w-input-capability
 
The GeForce RTX 3090 Ti debuted the new ATX 16-pin power connector for graphics cards, which minimize the cable clutter in your case, while meeting the growing power demands of graphics cards as Moore's Law buckles. During our reviews of the RTX 3090 Ti, we noticed that a handful graphics card PCBs had provision for a second 16-pin connector (implying that the first one with a maximum of 600 W of power delivery is maxed out).

GALAX debuted the first graphics card with two 16-pin connectors, a theoretical power input capability of a whopping 1200 W. At first we thought this is an exercise in absurdity, until we took a close look at our numbers again. Currently, ATX 3.0 PSUs with 16-pin connectors are extremely rare, and so every NVIDIA board partner is required to include an NVIDIA-developed adapter that converts three 8-pin PCIe power connectors to one 16-pin. Three 8-pin connectors only add up to 450 W, whereas in our testing we noticed that some of the cards were peaking well beyond 450 W, despite using this adapter.
 
This is where GALAX's idea of a dual 16-pin connector begins to make sense. Two 16-pin connectors mean the inclusion of two cable adapters, for a total of six 8-pin inputs, and an input capability of 900 W when using 8-pin PCIe connectors. The GALAX HOF series targets the crème de la crème of the overclocking community, where a stable power delivery is crucial to achieve record-breaking OC feats.

As for the power limits, officially the GALAX RTX 3090 Ti HOF has a power limit of 480 W, but a special BIOS-based P-mode activates 516 W power limits (something way beyond the capability of three 8-pin connectors), and hence the decision to go with a pair of 16-pin connectors.

Wow, that is a lot of power. 
 

Maybe this card and the future lines can be judged by the revolutions per minute of your electric meter instead of frame per second.

516w is more than 3 8 pins but not when you factor is the power from the 75w pcie slot. 150+150+150+75=525. EVGAs last 2 kingpin cards have been 520w cards with 3 8 pins. The inclusion of the 2nd 16 pin (also seen on the new 3090 Ti kingpin) has to be for XOC bioses.

“Something way beyond the capability of three 8 pins”

No. Just no. Please please please stop saying that. Capability and rating are two vastly different aspects.

The rating of three 8 pins would be 450w, but it has been shown repeatedly that LN2 cooling can pull more than 1000w on three 8 pin cards, so 516w.. that is nowhere, even remotely close, the capability of three 8 pin connectors.

So, please for the love of what ever deity you choose, stop saying this… it’s wrong. The cables are far more capable than they are rated for, which is why NVidia had two 6 pins, only a 150w rating, going to the 12 pin connector on the 3090 and below. Two of the pins on each connector were sense pins, and most likely unused, or they were wired to other cables, and still not used properly.

Michapolys
It depends on wire gauge, length and pins. Some combinations are actually limited close to 150 watts.

Anyone buying a 2000+ GPU shouldn’t be running low quality cables.