PSU Question

[1337leet]

Hello guys,

I use a Seasonic Focus GX850 for my rig.

The PSU has 4 8-Pin Connectors.
Each cable seperates in 2 8-Pin connectors.

I wanna run a 3090 (2x8Pin) a 3080 (2x8Pin) and a 3080 (3x8Pin).

Is it okay to use one 8 Pin PSU Connector which seperates in two to power one card?
That would mean up to 310 watt on one 8 Pin PSU connection.

That would be maybe 250 because 60 come from the connector.

Or do I need to run 2 seperate 8 Pins to each card?

[1714125098]

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[1714125098]

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[1714125098]

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[miner29]

Good way to melt you wiring, 

Max per cable chain for the whole chain is 285watts. 

You are exceeding that...this is melting and fires start.

See here for cable limitations...there are no shortcuts.....just shorting....

https://www.gpuminingresources.com/p/psu-cables.html

[1337leet]

285 is not exceeded.
It‘s 310 for the whole card and 50-60 from the Slot. So only 250 from the wires

[rdluffy]

You have 3 power hungry GPUs, in my opinion, you should use at least a 1000w PSU Gold rated

Each 3080 can consume 250w from the wall, and 3090 probably 280w, so 780w constantly
If your cards go the default due to a system failure, you'll use more than 850w easily, your PSU will turn-off due to overload

Here's a good source from seasonic:

https://knowledge.seasonic.com/article/8-installation-remark-for-high-power-consumption-graphics-cards

This is the recommendation:

[philipma1957]

okay funny he should ask. as I have 2x 3090 with 1x 3070

and I think it is a seasonic focus. 850 watt

my 3090 gear use  3 jacks  each and my 3070 uses 2 jacks.

so  1 cable and 1/2 cable to one 3090

and 1 cable + 1/2 cable to second 3090

and 1 cable to 3070


I pull 259 + 259 + 119

the  full rig is 677

let me check if it is the 1000 watt model.

it is the 1000 watt model

I have 8 pcie plugs across 4 cables

now if you are really slick on this psu you can adapt the  molex cables  a pcie cable.

https://www.amazon.com/Cable-Matters-2-Pack-8-Pin-Inches/dp/B01DV1Z428/ref=sr_1_3?dchild=1&keywords=molex+to+pcie&qid=1617202991&sr=8-3


this would allow

9 pcie plugs across 4 pcie cables and 2 separate molex cables.

Still I pull 677 and my kill a watt says 714 watts on my 1000 watt focus with 2x 3090 and 1x 3070. and my seasonic feels hot to the touch.

So I do not think the op can safely run 2x 3090 and 1 x 3080 on the 850 watt model

as I am having a hot 1000 watt with 2x 3090 and 1x 3070

[FP91G]

On the Seasonic Focus GX850, I would connect 2 video cards 3090 and 3080 (3x8Pin) motherboard, and for another video card, you need to buy a second power supply and a power supply synchronizer.
Or buy a 1000 watt power supply, and use Seasonic Focus GX850 for another farm, for example, for 5x1660

[mak013]

The main problem is not how to connect these GPUs. The main problem that this PSU is not enough for these GPUs. You need at least 1KWt PSU.

[batsonxl]

The main problem is not how to connect these GPUs. The main problem that this PSU is not enough for these GPUs. You need at least 1KWt PSU.

Yes agreed that psu will not last long under that load.

[miner29]

285 is not exceeded.
It‘s 310 for the whole card and 50-60 from the Slot. So only 250 from the wires

Each CHAIN...doesnt matter if its 1 / 2 /3 connectors on that wire chain from the psu it is limited to 285watts. 

3090 TDP 350W
3080 TDP 320W
3080 TDP 320W

Per Techpowerup.

Thats 990W just to GPUS.  PSU is 850W.  You have the potential to overload the PSU for sure.  Get a 1000W or bigger or dont run all 3 off the single psu. 

The GX850 comes with 3 dual PCIe cables 6 connectors....you have 7 plugs not counting risers. 

[philipma1957]

285 is not exceeded.
It‘s 310 for the whole card and 50-60 from the Slot. So only 250 from the wires

Each CHAIN...doesnt matter if its 1 / 2 /3 connectors on that wire chain from the psu it is limited to 285watts. 

3090 TDP 350W
3080 TDP 320W
3080 TDP 320W

Per Techpowerup.

Thats 990W just to GPUS.  PSU is 850W.  You have the potential to overload the PSU for sure.  Get a 1000W or bigger or dont run all 3 off the single psu. 

The GX850 comes with 3 dual PCIe cables 6 connectors....you have 7 plugs not counting risers. 

 My 1000 watt  seasonic model is pushed to a point of always feeling warm to the touch.

I clocked my 2x 3090 low
I clocked my 1x 3070 low

less power than 2x 3090 and 1x 3080 for sure.

with a better psu the 1000 watt not the 850 watts and I can tell you the psu feels pretty warm to the touch. my guess is he will not be able to run them.

I have 9 seasonic focus psu's

850 gold , plat

1000 gold , plat


they all prefer 50-60% of load vs 70-80%

this 1000 watt is at 677 software and 714 kwatt meter which is 67.7%-71.4%. and it is stressed enough for me to think about altering this build.

[adaseb]

I hate PSUs that have a 2 PCIe 8 pin in series. I had a few of these PSUs in the past and basically I connected it before to 300 Watts GPU powerhogs and basically I think I had issues with half of them melting. Where it melts is almost always the +12V pin which runs in series to the other 8 pin PCIe connector.

The hints that they were melting was that the GPU would crash randomly, I would reboot it would work fine for a bit and crash again. Finally when I decided to replace the GPU, the PCIe connector was basically stuck in the GPU, was almost impossible to seperate it. And upon inspection, the 8 Pin +12V which is in series with the other connector on the GPU had melted.

No idea why its legal to sell PSUs this way. Maybe if it was 2 PCIe 6 pin connectors but not 8 pin.

[vuli1]

and what was the brand of the psu? if I may ask.

[1337leet]

I needed to run one 3090 with one cable.

Like the "Standard" option mentioned in the picture above.

Until now (for 2 days) it's all fine. But I ordered another 8 Pin Cable from Seasonic so I can run 2 seperate cables.