I’ve got an EVGA 3080 ti FTW3 ultra and a Corsair rm750x that only has 2 PCIE 8 pin power cables. Each PCIE cable comes with 6+2 pin pigtails attached. Using both PCIE cables, can I also use one of the 6+2 pigtails for the 3rd 8pin on the 3080ti FTW3?

I would get an 850w psu min with this card and run 3 cables 
EVGA has a good sale going this weekend

You should be able to run it by using the split cable in PCIe #3 (8 pin closest to the end of the card) just don't really try to overclock it. The Corsair PSU you have is a good unit and should be able to cope with it but I would advise a higher spec PSU in the near future. 

Just throwing this out there. I’ve got a 9700K paired with a 3080 Ti FTW3, and they’re powered by a 750W 80+ platinum PSU. Haven’t had any issues. I’ve also got a 9900K that’s also paired with a 3080 Ti FTW3 that are powered by 1000W 80+ titanium PSU. Something I’m considering, however, is the fact that Alder Lake CPUs are quite power-hungry. The 12900K is reportedly drawing upwards of 330W under heavy load. With that in mind, it’s giving me pause about even my 1000W PSU given that my GPU can easily pull close to its 450W rating. AMD CPUs don’t seem to be as thirsty for juice, so that may factor in depending on what platform you’re currently using and with regard to future upgrades. If there’s one thing that’s somewhat future-proof because they last, it’s a PSU. So, make sure you choose one with plenty of headroom when it comes to power.

When it comes to powering your GPU, I’d run 3 separate PCI-E power cables to it if I were you. Like kraade said, you’ll be pulling more amps through a pigtailed power connector. Any licensed electrician will tell you why it’s a bad idea to use a 20A circuit breaker when the wiring is rated for 15A. The same principal applies to the wiring of your PCI-E power cables. A pigtailed cable will run rather hot and that could cause problems or failure over time.

Run 1 and 3 on the same cable for now, keep 2 (middle) on the single cable, get a better PSU and don't overclock/increase power limit for now.

I bought a rmx 850 last week and its sounds like it has exactly the same setup. 2 PCIE cables each with a pigtail. Luckily I have a 3070ti for now so i can run a separate cable for each, but the idea of having almost 300 watts from a single connection sounded a little much.
 
My ancient AX850 from 2011 had 4 separate 8 pins with proper connections. Kind of felt like a downgrade lol

Thanks everyone. I’m not even going to try using the rm750x for fear of melting something. I ordered a RM850x but 2018 variant that comes with 3 PCIE cables. The new 2021 variant of the same psu comes with only 2 PCIE cables, but it does come with 3 CPU cables! Huh? Lol

Well that's just stupid.  Looks like you have to step up to the RM1000x to get 3 cables.  Might be worth it for future proofing when 450w is the reference PL.  lol

al2jzge
I’m not even going to try using the rm750x for fear of melting something.

You would not melt anything.

talon951
Well that's just stupid.  Looks like you have to step up to the RM1000x to get 3 cables.  Might be worth it for future proofing when 450w is the reference PL.  lol

Monst3r
Yeah i was really thrown off by the 3 EPS 8 pins. But yeah good call, might return my Rmx 850 2021 model and get something different as im hoping to eventually step-up to a 3080 as well and while im sure its fine to double up on one, id really rather not.

Yeah return it and write Corsair CS a sternly worded letter.
 
I looked far and wide for any MB's that support 3x EPS, they are ultra rare.  Granted, you can buy extra Corsair PCIe cables.
 

demon09
 
? my rm 850x has 3 seprate 6+2 pig tail cables so not sure what you mean by stepping up to rm1000x for 3 cables I belive the 1000w has 4 of them 

 
https://www.tomshardware....21-power-supply-review
 
I didn't believe it either.

I have The 1000 G Evga power supply and run 3 separate cables. No issues for me that way

kevinc313

talon951
Well that's just stupid.  Looks like you have to step up to the RM1000x to get 3 cables.  Might be worth it for future proofing when 450w is the reference PL.  lol

Monst3r
Yeah i was really thrown off by the 3 EPS 8 pins. But yeah good call, might return my Rmx 850 2021 model and get something different as im hoping to eventually step-up to a 3080 as well and while im sure its fine to double up on one, id really rather not.

Yeah return it and write Corsair CS a sternly worded letter.
 
I looked far and wide for any MB's that support 3x EPS, they are ultra rare.  Granted, you can buy extra Corsair PCIe cables.
 

demon09
 
? my rm 850x has 3 seprate 6+2 pig tail cables so not sure what you mean by stepping up to rm1000x for 3 cables I belive the 1000w has 4 of them 

 
https://www.tomshardware....21-power-supply-review
 
I didn't believe it either.

ah what the hell the new 2021 rmx 850 is only has 2 pcie 6+2 cables.... but instead has 3 4+4 cpu cables thats an odd change from the older version having 2 cpu 4+4 cables and 3 pcie cables. 

I always like to have a bit more power myself. When I saw a sale on a Corsair 1000 watt PSU I bought it right away.