[SOLVED] Is it a bad idea to power 4 x RTX 3090s using only 8 original 8-pin VGA power cables from the PSU while adding 4 x "8-pin to 2 8-pin power splitters"?

SeriousGaming101

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Mar 17, 2016
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Hello all,

I am currently mining on 3 RTX 3090s (Each card requires 3 8-pin power connectors), so that is 9 power connectors TOTAL from the PSU.

My PSU is a EVGA 1600 watts Titanium SuperNova Power Supply (It has a maximum of 9 VGA cables for powering the video cards)

Currently, mining only draws about 300 watts for each video card and the entire PC is drawing 1050 watts from the wall.

I WANT to add a 4th RTX 3090 to my PC mining rig AND USE THE SAME PSU for ALL 4 GPUs.

However, the problem is that, having 4 RTX 3090s would require 12 of the PSU's 8-pin power connectors. (But the maximum the PSU has is 9.)

So my idea is to buy 4 of these 8-pin to 2 8-pin power splitters, something like this:
https://www.amazon.com/JacobsParts-Express-Power-Splitter-Cable/dp/B07611QXG4

After giving each GPU a cable power splitter, all 4 RTX 3090s would then have 3 8-pin power connectors added to them.

I would have to use only 8 of the original 8-pin power connectors hardwired from the 1600 watts EVGA PSU and would have 1 original power connector left over.

I think the total power draw for 4 x RTX 3090s mining would be 1350-1400 watts from the wall (out of 1600 max)

Do you guys think that this is a bad idea? Can only 2 original 8-pin power connectors hardwired from the PSU able to continuously power 1 RTX 3090 each? (After giving them a power splitter which turns them into 3 8-pins?)

How much power(watts) can 1 single original 8-pin power connector cable hardwired from the PSU able to give to the GPU?




If this is a good idea, can you guys recommend me (using a link) the best/highest quality "single 8-pin to 2 8-pin power splitters" money can buy in the market today?


Thanks
 
Last edited:

vov4ik_il

Respectable
The short answer is "NO".
The long one is (corrected to spec):
  • Each +12V wire/pin in PCIe connector is rated to 8A or 9A which yields (8*12)=96~108W
  • Every 8-pin PCIe has 3 +12V lines providing (96*3) 288W
  • Splitters are totally not recommended for high-current components
 
Last edited:

vov4ik_il

Respectable
The short answer is "NO".
The long one is (corrected to spec):
  • Each +12V wire/pin in PCIe connector is rated to 8A or 9A which yields (8*12)=96~108W
  • Every 8-pin PCIe has 3 +12V lines providing (96*3) 288W
  • Splitters are totally not recommended for high-current components
 
Last edited:
Oct 9, 2020
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I WANT to add a 4th RTX 3090 to my PC mining rig AND USE THE SAME PSU for ALL 4 GPUs.
You're going to have to add a second psu. Even with 3 3090's or maybe even two in some cases, you would need a second psu. Per rtx 3090, I would recommend 850-1000w of power, so you would probably need two 1600w psu's for 4 rtx 3090's. While one 3090 will draw around 750w, voltage spikes and overclocking isn't taken in to account, so if you want a reliable system the delivers clean power, you will need what I said above.
 

Zerk2012

Titan
Ambassador
That's fairly common for mining but in your case I don't think I would run a PSU under that kind of a load 24/7.
I would probably add another PSU with enough watts to run 2 cards in case you wish to add even another in the future.

Their easy to hook up using a 24 pin connector like this to turn on the 2nd PSU.

https://www.amazon.com/Mega1Comp-Exclusive-Splitter-Motherboard-Adapter/dp/B07CKJV5X5/ref=pd_di_sccai_3?pd_rd_w=Jz0vI&pf_rd_p=c9443270-b914-4430-a90b-72e3e7e784e0&pf_rd_r=PVF20N0E5Z3A175NAGYD&pd_rd_r=b7dfb980-5729-4125-bd31-92c139120ba5&pd_rd_wg=mEYys&pd_rd_i=B07CKJV5X5&psc=1
 

helper800

Distinguished
There is no slot in my Thermaltake Tower 900 PC case to mount the second PSU.
So this is the reason why a lot of people who mine don't use enclosures for their mining rigs. If you want to add another card I would recommend getting a test bench or open case to put the rig in to add another PSU. If you prefer your mining to be done within cases then I would make another mining rig for the 3090. At least with another mining rig started you could get even more cards for even higher rates. It all depends on what your end goal with mining is, you know, besides making money mining.
 

SeriousGaming101

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Mar 17, 2016
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The short answer is "NO".
The long one is (corrected to spec):
  • Each +12V wire/pin in PCIe connector is rated to 8A or 9A which yields (8*12)=96~108W
  • Every 8-pin PCIe has 3 +12V lines providing (96*3) 288W
  • Splitters are totally not recommended for high-current components
I'm confused, if "Every 8-pin PCIe has 3 +12V lines providing (96*3) 288W", then wouldnt 2 8-pins be enough? (Because 2 x 288W = 576W) And each GPU only needs about 300 watts for mining?...
 

InvalidError

Titan
Moderator
300W > 288W, try it and you will end up here.
While the PCI-SIG only rates AUX cables at 150W, the weakest MiniFitJr pins support 9A each so a properly made cable can safely handle 300+W at 12V, 450W when using the 13A high-current variant. That's why modular PSUs only need a single 8 pins connector to feed a 2x8-pins cable.

The reason the connector got burnt in that other thread you linked is likely an incorrectly crimped connector since all the burnt pins are those with doubled-up wires for the daisy-chained 2nd connector, an intact properly made cable wouldn't come anywhere close to melting at only 300W total load.
 

vov4ik_il

Respectable
pins support 9A each so a properly made cable can safely handle 300+W at 12V
9A if only 2 wires in use (PCIe 6) or 8A if there are 3 (PCIe 8, due to heating), per Molex standard. Can you make one that handles 50A? Sure, but that is not standard and the mating connectors in PSU or the card may not handle it well.
In that other thread, the guy used aftermarket cabling, and here the guy tries to use splitters.
Not to mention that the card will likely have current steering problems due to uneven supply voltage as a result of those splitters.

Without going further into details, I would not recommend doing it.
 
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