dual RX3080 in a T5820 with a 950W power supply?

A stock RTX 3080 FE will use 320W under full load.  Most other cards come with a factory overclock, that can push the power draw to around 400W

Dell lists the maximum supported GPU configuration and 600W total or 2x 300W cards.  I'm going to guess that your computer comes with 2x 8 pin GPU cables (with a 2x 6pin adapter plugged into each 8 pin)  Your RTX 3080 cards will either have 2x 8 pin connectors each. (FE cards have a 12 pin with an adapter that uses 2x 8 pin connectors)

Any way you look at it that machine will only support a single RTX 3080.  On a side note, these Precision towers are designed with "Blower" style Quadro cards in mind.

Not sure about V7594 950W psu. I think you need 1300W PSU to run 2X RTX 3080

Ask @DELL-Chris M  what the power supply options are and have him include the cable options for the video cards.

If you have 625W or 825W power supply its definitely not supporting 2 X 300W cards.

It takes 2 SIX PIN connectors to make ONE 8 Pin Connector.

Number of PINS DOES NOT MEAN PLUG IT ANYWHERE YOU WANT AND FORCE IT IF IT DOESNT WANT TO GO IN.

CPU connectors are NOT GPU connectors.

They are keyed to prevent this mistake but some users FORCE it in and DESTROY everything in a FRY and DIE motherboard gpu FIRE situation.  SMOKE BANG POOF! and everything is dead.

Note the number of 12v Wires for ONE 8 pin PCI-E power connector.

If you have 2 x 375w video cards it takes Four SIX PIN connectors into 2 adapters for dual 6 pin to 8 pin PER RTX 3XXX video card with DUAL 8 pin to  MINI 12 pin connector. So you would need  Eight SIX PIN connectors to go into FOUR DUAL 6 TO 8 ADAPTERS for 2X RTX 3080 cards. Tapping power using sata or other connections or doubling up connectors to get more DOES NOT ADD MORE POWER to your power supply and IS NOT SAFE from a fire safety standard. UL94V fire safety spec is VERY specific.

This has nothing to do with the power supply watts has to do with fire safety for 18 awg wire and molex connectors.

12v 18 amps is a hard limit for the 4 wires on any connector.

12v 6.25 Amps is the rated spec for ONE six pin connector.

12v 12.5 Amps is the rated spec for ONE 8 pin connector.

https://i.dell.com/sites/csdocuments/Shared-Content_data-Sheets_Documents/en/us/Precision-5820-Tower-Spec-Sheet.pdf

@JamesJAB1

"I'm going to guess that your computer comes with 2x 8 pin GPU cables "

That guess is wrong.  Stock unit comes with 1 CABLE to the power supply daughter board dual 6 pin or no cable whatsoever with a 75W card.

@DELL-Chris M   might have more information.

The T5820 came with one RX3080 and two 8 pin GPU cables from our Dell supplier (I disconnected the left GPU cable to take some pics).

I have limited the GPUs to a maximum of 240 watts. The question I have is, could I power an RX3080 with a single connector on the PSU if I use a 2x8 pin Y cable?

GPU cable on PSU side (on GPU side cables are standard):

PSU:

The SPMD (Spare Parts Master Database) doesn't list any 1300W PSU for the Precision 5820/5820 XL?

Precision 5820/5820 XL validated PSU =
WGCH4 950W Acbel, EPA, E-Star
CXV28 950W Chicony, EPA, E-Star
V7594 950W Delta, EPA, E-Star
Y097X 425W Delta, EPA, E-Star
3W8F7 425W Liteon, EPA, E-Star

The Graphics section list =
Dual 150W + 150W (total 300W)

@DELL-Chris Mthanks for your time. Do I understand you correctly that the two GPU connectors on the PSU board are only 150 watts each?

The notation in the training page shows =

Single 225W
Single 225W + Single 75W ( total 300W)
Dual 150W + 150W (total 300W)

I think that the slot in a single video card scenario uses 225W.

Slot 1 = PCIe x16 wired as x8 Gen 3
Slot 2 = PCIe x16
Slot 3 = PCIe x1 Gen 2
Slot 4 = PCIe x16
Slot 5 = PCIe x16 wired as x4 Gen 2
Slot 6 = PCI

Now, to add to the discussion/debate, we see this on in the Precision 5820 Owner's Manual page 88 =

Hi,

I'm thinking about adding 2x Nvidia P40s to my 5820, I would like to know "how" to get the 2x 300W?

From the below, it is unclear to me which ports to use.

Single 225W
Single 225W + Single 75W ( total 300W)
Dual 150W + 150W (total 300W)

Will the 2x 8 pin connectors do a max/total of 300W or more??

And if the 2x 8 pin is limited to 300W, where do I get the other 300W from for my other GPU? 

Is this from the 10pin connector?

I've tried searching for any "power output" related docs for the 5820, but I couldn't find any :(

Thanks a lot!

I'm caught up to speed on this thread.  I am also trying to run dual 2080ti cards in a dell 5820 with a 950w power supply.  I will be using this strictly for gpu based LLM inference, so CPU usage is negligible.  

On page 117 of the owners manual, it says that PCIe slots 2 and 4 are 300w capable, and 250w each if using more than one MEGA.

Soo... if i use a splitter on the current 2 x 8 PCIe power, so each card is getting 2 x 8PCIe at 75w each plug, 150w, per card... shouldn't this be ok if the power draw of each gpu is 250w?