Question x2 PCIE cables for 4090?

[Naxo556]

Hey,
So I read how everyone suggesting using separate PCIE cables for every individual GPU 8Pin slots, but currently, I'm using x2 3090 gpus, each connected by x1 PCIE cable.
I'm planning to add 4090 to a system (3D rendering), so wondering if cables won't start a meltdown (lots of fearmongering around).

Current PSU "be quite dark power pro 1500w".

Plan.
(GTX 960 is not used and it's not drawing much power, I just use it for photoshop to save vram, works at 0-5% usage at most)

Safe?

 

[Lutfij]

Welcome to the forums, newcomer!

How old is the PSU in question? You should be getting an adapter with the card you purchase that allows you to adapt 8pin PCIe connectors(3 or 4 depending on what card you end up buying) to the 12VHPWR connector going into the GPU.

 

[Naxo556]

Welcome to the forums, newcomer!

How old is the PSU in question? You should be getting an adapter with the card you purchase that allows you to adapt 8pin PCIe connectors(3 or 4 depending on what card you end up buying) to the 12VHPWR connector going into the GPU.

I brought PSU in 2022 or early 2023. It's not some old model, it's still available on sale around the stores.
And I know about the adapter-connector, my worry is would this PSU will power multiple GPUs just fine, some being connected on a single PCIE cable (x1 cable for x1 GPU) and 4090 on x2 PCIE cables.

 

[RodroX]

You want to add a RTX 4090 to your current 2x RTX 3090?

Or are you replacing one of the RTX 3090 for this new RTX 4090?

Im asking because I do not know what motherboard do you have to have enough room for all this cards plus their cooling solution, and because both of your RTX 3090 needs around 400watts each while fully loaded (could be a little more), thats at least around 800 watts, then you need to add extra ~450 watts or more, depending on the model, for the RTX 4090, so that alone its about 1250 watts of load

And to all that you need to add the other components of the system like the CPU, which may consume also a fair share of energy (not as much as the GPUs of course) depending on the model and the load.

Perhaps you should list the rest of your system for everyone else looking.

 

[Naxo556]

You want to add a RTX 4090 to your current 2x RTX 3090?

Or are you replacing one of the RTX 3090 for this new RTX 4090?

Im asking because I do not know what motherboard do you have to have enough room for all this cards plus their cooling solution, and because both of your RTX 3090 needs around 400watts each while fully loaded (could be a little more), thats at least around 800 watts, then you need to add extra ~450 watts or more, depending on the model, for the RTX 4090, so that alone its about 1250 watts of load

And to all that you need to add the other components of the system like the CPU, which may consume also a fair share of energy (not as much as the GPUs of course) depending on the model and the load.

Perhaps you should list the rest of your system for everyone else looking.

It's open rig case+using raiser cables. So fitting and cooling is not an issue.
And CPU (i5 11400F) works minimally during rendering.

4090 and x1 3090 will use PCIE 16x Riser Cable
The other 3090 will have to use Pcie Riser 1x PCIe as per motherboard limitation.

 

[geofelt]

At one time, two 6+2 connectors on a single cable was normal.
But, that was mainly intended to connect to a 8pin plus 6pin gpu.
When dual 8 pin graphics card appeared, some(like me) used one cable to simplify cable management.
But in the psu manual, it merely said not suggested.
Yes, it worked seemingly ok. In my case, I never puished the gpu. Regardless, I followed advice and now use two cables.
But, there were reports that the single cable got overloaded with full power draw and failed.
Moving on, seasonic now does not supply two heads per cable, but only one, resolving that issue.
Here is what the back panel of a top psu now looks like:
https://www.newegg.com/seasonic-prime-px-1600-1600-w/p/N82E16817151257
It will include 8 individual 6+2 cables which is really what you want.
With so much invested in your rig, you may want to upgrade your psu.