@paper plane​ 

I'm asking any seller online about their 10pin to 8pin and 8pin to 8pin for t5810 if I can use them on my t5810 for powering a modern gpu (amd rx 6800 xt in my case), all of them give me a negative answer.

I don't know, maybe they simply want to avoid any responsibility, since these workstations (and cables) are officially made for working with quadro cards.

However I don't know if it's a good idea to just try a couple of them, I wouldn't want to damage the hardware.

So, I have the same question as lukaszm2109. I need to know both 8 to 8 and 10 to 8 compatible cables.

@lukaszm2109 Did you find any solution??

on the 5810 there is a 10 pin "AUX CPU" power connector on the power distribution board. This is the same as on the 5820 series of Dell PC's and i was able to get some cables off of ebay - listed as 10pin to 2x 6+2pin for the 5820, that fitted the 5810.

so - final configuration looked like:-

one connector was a 6 to 8 pin adapter on one of the 6 pin normal PCIe aux power connectors that the 5810 already has,

the other connector from this 10pin to dual 6+2pin adapter, for the second 8pin PCIe power connector

i had been running a Gigabyte Vision OC RTX3080 10gig card like this with a 685Watt power supply for a few years now.

last year I managed to land an Asus TUF Gaming 3080ti 12gig card, so setup my son with my gigabyte card in his 5810 with the exact same power setup i had above that worked fine. he's been rolling with that machine being switched on for 24/7 for months now with no issues. again 625Watt power supply.

However, with my new to me 3080ti I and had some crashes. i was able to narrow it down to a particular type of shadow rendering in games, and changing the 685Watt PSU to a 825Watt PSU seemed to help reduce the crashes a bit, it's still not 100%. I'm not sure its power related as GPU-Z says that both cards pull about the same 350Watts, or if this card is actually the problem is some otherway. i have no way to test if this card is good in anything else..

I tried to get a 1300Watt PSU to fit a 5810 from ebay/China for about £100, but funnily enough, it didn't fit. so i just paid £100 for what effectively feels like e-waste. ergh.

my next option is to try to land a cheap Dell 5820 machine with a 950Watt PSU. advantage here is that apparently the CPU's it takes are windows11 compliant, and i can use the ram/drives and of course graphics card, out of my existing 5810.

however, do i keep trying to kludge together something that may work, or actually it down in the current climate and try to build something new that will work to support this RTX3080ti - that i'm not sure is 100% ok... the trials of life! 

@paper plane​ Thank you for the answer.

I bought the cables from the guy on reddit, he has a lot of review, all positive.

He said that the pcie and cpu2 connections are powered from the same line on the 685 watt psu, thus, one split cable from pcie-vga alone or using also the cpu2 connection, the max power you can draw remains 150 watt (+75 = 225 watt total).

With a 825/1300 watt psu you get separated lines, so using both connectors you can draw up to 300 (+75) watt.

The 1300 watt psu has an additional line (but you need the modded board for being able to use it).

I'm waiting for the 1300 watt psu coming from China. They assured me it is appositely made for the t5810. I bought it on ebay, they accept return. We'll see.

Please let me know if you have found a resolution as of now? We are having so much trouble trying to power a rtx 8000 on a T7810 with a 825 power supply with only an eight pin vga port on the power expansion board even though we have split it into a dual six back to an 8 pin connector to the gpu along with powering the six pin with a sata to six pin. 

Its not 1100W its   DELL 1300W Power Supply

@DELL-Chris M   might have more information.

PN: MF4N5 H3HY3 V5K16 6MKJ9 T31JM

https://www.amazon.com/1300W-Power-Supply-Precision-Workstation/dp/B0777QSTC2

MF4N5 H3HY3 V5K16 6MKJ9 T31JM

There is a drop in 825W replacement for the Power supply and specific proprietary cable that goes to the power supply board.

There is also a 3rd party cable

YMMV

https://www.amazon.com/COMeap-Power-Adapter-Cable-13-inch/dp/B07HCYDK5K/

Dell is dual 6 pin not dual 8 pin. D92C9

https://www.amazon.com/POWER-SUPPLY-PRECISION-T5600-T5610/dp/B01N3VG801

https://www.amazon.com/COMeap-Power-Adapter-Cable-13-inch/dp/B07HCYDK5K/

Precision 5810 power supply part numbers:

YFY1V - 425W PSU

VDY4N - 685W PSU

RHHKV - 825W PSU

Power supply extended card part number is M6NP2:

It goes here ( this is a picture with the power supply removed

splitter cable part number D92C9:

https://www.amazon.com/COMeap-Power-Adapter-Cable-13-inch/dp/B07HCYDK5K/

For this model, there were two 1300W PSU =
V5K16 Delta EPA (Precision T7910/T5810)
0T6R7 Delta EPA (Precision T7910/T5810)

MF4N5 Delta EPA (Precision T7610/R7610)

Did you ever get this working? I'm attempting to do something similar but having an impossible time doing so. My PC is constantly crashing under load, despite a new power supply (825W FT7T6), new CPU, new RAM, and fully tested GPU. At this point the only explanation I have is that the multi rail psu design is causing it, and I need to just replace my mobo with an x99 or something and just scrap this whole idea already. I cannot figure this out for the life of me.

Funnily enough, i'm doing the exact same thing as the Original Poster. Been running a Dell precision 5810 (685W PSU)  with 4x16gig, a 10gig ethernet card, and an NVMe to PCIe adapter as boot drive. Graphics card was the original Nvidia Quadro M4000-8G. so last year in September i got on the pre-order list for an RTX3080. it didn't arrive until February. but whatever. i have something solid to run on this box.

So the stock config for the PCIe aux power is 2x6pin. first i tried a pair of 6-to-8 pin adapters. no dice. wouldn't get past bios post. then reading up on it, there is an AUX CPU power on the PSU distribution board. so got a pair of cables off of ebay, one that has 2x8pin aux off of the original PCIe aux power port on the distribution board, and a 2x8pin aux off of this other AUX CPU power port. so i ran one 8pin power from each pair - each 8pin port on the GFX card getting it's "own" supply.

this seemed to work fine for a few months, but i never really turned my machine off ever, then a windows update caused a reboot, and it either couldn't get through bios post - or the machine spins up, boots, but the screens are dead. it's exactly the same as when i tried to boot the machine with a PSU feed that wouldn't support the card.

so i figure its a power issue. and further reading leads me to believe that the 825W PSU has a different distribution board? but i'm not 100% on that...

right now as it stands, having retired my Quadro M4000-8G to my old precision T3610, i'm reduced to a pair of quadro NVS310's to drive my three screens till i can get this sorted out. either i find an 825W psu and it works as a straight swap, or i figure out some external GPU PSU heath-robinson affair.

however, when it was running, it was unburstable. furmark left for a day or so untill boredom set in or i wanted to do something else. GPU-Z reporting anywhere from 320Watts to 340Watts GPU power draw. hours of cyberpunk2077... i figure i've crossed a line somewhere and something is just saying "no" right now...

ok, so a note to not checking your work...

the 8pin plugs that i have feeding my graphics card are split 6+2 pin things, where the 2pin "clips on" to the side of the 6pin plug, making it an 8 pin unit that plugs into the graphics card. i hadn't clipped the 2pin bit onto the 6pin plug of both plugs properly, so they weren't sitting in the power socket on the graphics card properly. the machine would fire up, just no display.

after checking all my connections, and that one 8pin power feed was coming from the PCIe power socket on the PSU's distibution board, and the other 8pin feed was coming from the AUX CPU power socket, and that the full 8pins were seated in the graphics card, my machine boots just fine.

so i'm running a Xeon E5-1650v4, 64gig ECC ram, a 10gig ethernet card, a PCIe to NVMe adapter with a 1TB SSD, and lastly an RTX3080. all hanging off a 685W PSU. everythings ticking along just fine so far...

ok, so, longer term living with this setup. gaming with this machine on the 685W PSU, with a 3080 being fed one 8 pin PCIe power from the AUX CPU power socket, and the other 8pin PCIe power fed from the normal PCIe feed off the PSU. this works. and is seemingly fine. HOWEVER.

the machine will crash from every few days, to maybe get a week, maybe two weeks of 24/7 running. this is not mining machine. i just leave it on all the time as this is my work from home daily driver.

turns out there is a thing called "transient load" with GPU's where they can pull up to twice their rated power requirements.  this was ok with 10 and ok-ish with 20 series cards. but my 3080 could pull up to 700Watts for a "blip". i can't pinpoint if this is the issue, but i'm hunting for a PSU swap that could give me some headroom to cope if this is the case. the 5810 doesn't turn off completely, just freezes, then hard resets. i hope that's the "server" nature of it's PSU at least not letting the machine fall flat on it's face.