Here in Australia it's summer so the card would hit 79c, but never went under it's advertised 1725Mhz.

He's the kicker, it's a underperformer bigtime, even with the Hybrid kit keeping temps well under 60c, it'll downclock to 1725Mhz (depending on the load/game) due to smashing the power limits, even with a decent overclock.

There was this thread about cross flashing the BIOS if you're game.
https://forums.evga.com/3...-to-Hero-m3192487.aspx

NewSlang22
So it's basically worse in performance and cooling than FE?

Performance yes, the FE is 400w I believe, cooling is a tad better, we were having 40c (104F) days here in Australia.
I also only run the XC3 with the stock cooler for a day before slapping the Hybrid kit on it.

NewSlang22
Realistically, when running 4k with a 60hz monitor, would using this Bios flash or even getting a different 3090 altogether be worth the trouble?

No, maybe 2 - 4fps increase.

NewSlang22
Hello, I just acquired a a EVGA RTX 3090 XC3 Ultra and I was just wondering if any XC3 users can inform me about the performance of this particular card as there seems to be very little information available. One thing I've read is that the 8 pin power connector limits power draw to 366 watts, and consequently limits the clock speeds of the card significantly. Also how cool does this card run on average when in idle and under load? Thanks!

 
Yes the performance is a tad lower than other 3090s, but it is a dual slot card and fits in my mini-ITX case which is why I bought it. I have a good cooling set up with 2x 120mm fans right beneath the GPU at the bottom of my case and temps have never exceeded 80C when using the "custom" fan profile in Afterburner. At idle it sits at about 25-30C. My GPU clock speeds range from 1725mhz to 1925-ish. Usually it hovers around 1825mhz I've noticed. It is a poor overclocker, I can only do +90 on the core offset. 
 
I've tried running other BIOS (the KFA 390 watt BIOS) and it did virtually nothing to performance of the card, so I re-flashed my original stock EVGA BIOS onto it. It isn't worth it, in my opinion. 

NewSlang22
Would you guys say that my Seasonic Focus+ GOLD FX750w PSU would be good enough to run the RTX 3090 XC3 Ultra for now? Would you recommend I upgrade to a 850w or 1000w PSU if I wish to flash the bios to utilize over 366w on the GPU?

I am using a Corsair SFX 750w platinum PSU and it has been fine. My CPU is a 9900K overclocked to 4.8ghz. I used a Kill A Watt and the most power drawn I found was about 620 watts when gaming (Cyberpunk, F1 2020, Borderlands 3 are some examples of games I play). I haven't had a single crash or error. To be safe I'd recommend an 850w PSU but you should be fine in the meantime with a 750w. 

NewSlang22
On that note of possibly upgrading my 3090 XC3 Ultra, would the Step-Up Program be a good option to get a FTW3?

If your case can accommodate it, why not? Depending on what you paid for the XC3 Ultra. I paid $1799 for it from another online retailer, I decided to enter the step up queue just because it's only an extra $70 plus tax for me. I can make a firm decision on it when the time comes (need to remove my bottom case fans from inside and put on outside bottom of case, or remove them completely to accommodate the GPU). 
 
Edit- if you opt to step up to the FTW3 Ultra, you may also want to just go with the 850 watt PSU. That's another issue I have to think about.