Nvidia recommends 750w PSU.  825w has that exceeded.

https://www.google.com/amp/s/www.pcworld.com/article/3575494/do-you-need-a-new-power-supply-for-nvidias-geforce-rtx-3080.amp.html 

Thanks for the reply sir.
But GPU needs 2x8pin cables coming from PSU which i dont have. I just have a free 8pin for PCI-e.
And if i use "8pin to double 8pin adapter" the system shuts down under GPU overload. Everbody suggests two seperate cables.
If i unmount the optical drive and the harddrives and i use a "double sata to 8pin adapter" maybe it would work. But i dont know it sounds risky to me using sata power for GPU.
So yeah, 825W looks enough but there is no proper tool to connect.

@_@_

Does this 1300 watt PSU work in the 7810? Is it safe?

There is no link or photo as to the PSU you're referring to.  If you're referring to a PSU speedstep recommends, then it's safe.

Hi Bro, can u pls specify, are u using 1300W PSU with Dell T7810?

I have T7810 with 825W PSU and want to change it with 1300W.

Speedstep hasn't been on this forum since mid-Sept. 2022.  I do know he knew what he was talking about as he owned Precision's himself.

@regonsite: Hello! I also have the same intention. Has anyone been running a 1300w power supply with MB T7810. Do they have video images to attest to that? Thank

The 1300w (10-rail) power supply uses a different power distribution board than the 825w (7-rail) or 685w (5-rail.)  The T5810 and T7810 boards have two 10-pin CPU connectors, one ATX connector and one 8 pin VGA connector.  You can use one of the CPU connectors to power a GPU with an appropriate cable.  This power distribution board will accept at most 7 rails of power from a PSU. You can plug the 1300w PSU into the board and it will work, however, you won't get more power from the unit than with the 825w - unless you change the power distribution board and associated wiring.

https://www.dell.com/community/Precision-Fixed-Workstations/T7810-with-1300W-power-supply/td-p/7761075

The above link provides more information on the difficulties in drawing the 1300 watts of power from the supply with the 5810/7810 distribution boards.

The T7910 has a power distribution board that can use all 1300w and could probably be swapped into a T5810 or T7810 with a significant amount of effort.  It has three 8-pin VGA connectors.

I'm no longer sure about my comment above about not being able to draw more power from the 1300w unit.  It likely depends on how the PSU connects to the power distribution board and how much power could be drawn from the 8pin connector and the 10pin connectors.  Each rail could supply up to 18A x 12V = 216w of power, up to the limits listed on the power supply.  In theory, you might be able to draw 1300w from 7 rails but it might be better for the PSU to have a max sustained power draw divided as evenly as possible among the 10 rails rather than letting 3 of them sit unused.  It's not clear to me how much could be drawn from one 10-pin connector or one 8-pin connector on the distribution board. 

I have a 1300w PSU running in a Precision 5810 that uses the same distribution board as the 7810.  Right now I don't have a high-powered video card to test it out a max power draw scenario but the 1300w unit powers my RTX 3060 with 1x8pin connector just fine.  I have noticed occasional coil whine from my unit and have wondered if that is caused from not using 3 of the rails or if the unit just sat unused too long before I bought it in the used market.