A photo just surfaced from a PC with a GeForce RTX 3090 installed, that is a Founders Edition card installed and we already knew it would be big, like 31.3 cm in length big. Actually it is tall as well at 13.8 cm. 

Basically an RTX 3080, just bigger! Not a big deal for most users that will buy one, but you need to be sure that puppy fits alright. Why so big? Well, PCB real-estate and cooling of course.  As you can see it has the single 12-pin power connector, connected with an adapter. The RTX 3090 is rated to be 350W on TGP. Below the photo that came from, yes of course .. the ChipHell forums via videocards. There is a warning, as the card looks a bit too shiny and does not have the expected chrome finish? 

But yeah it's a BFG alright :)

Yeah that GeForce RTX 3090 is one big dude!