Question 3 x 8-pin on Corsair RM850x & RTX 3090 ?

Jun 16, 2021
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Hi there,

I currently have a Corsair RM850x 80 PLUS Gold PSU and a RTX 2080 Super which are connected by 2 x 8-pin cables (both of which have an additional loose 8pin connection on the cable).

I'm looking to upgrade to an RTX 3090 (most likely the ASUS ROG Strix or MSI Suprim), but most of these require 3 x 8-pin connections. There's a couple of things I'm not sure of and want to check first though, as I don't have much experience with any of this.

1. Can I simply use one of the extra 8pin connections from the 2 cables to make up the 3 x 8-pin connection requirement? Is there any downside to this?

2. If I can't do that and I need to use a separate 8-pin connections for each of those, which slots on the PSU specifically should I be using? Are certain slots dedicated to the CPU, or are any of the five 8-pins on the PSU able to be used?

Picture of the available slots on the PSU: https://www.corsair.com/medias/sys_master/images/images/h2e/h09/8921435373598/-CP-9020180-EU-Gallery-RM850x-PSU-06.png

3. Will the 850W be enough to reliably run a RTX 3090? If it helps, my full system specs are:

MSI MPG Z490 Motherboard,
i9-10900k, RTX 2080 Super,
64GB DDR4 Ram,
1TB NVMe M.2 SSD,
8TB Storage HDD

Any help would be greatly appreciated, thank you!
 
Jun 16, 2021
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https://forum.corsair.com/v3/showthread.php?t=201374

I'm not sure but their a lot of power supplies that cant handle the power spikes of those cards.
They will get a huge power spike then the card hits the power limit and brings the watts back down.

If I was buying a 3090 I would probably go for a 1K watt power supply.
Thanks for letting me know!

In that case, if I were to upgrade to the following 1200W PSU for example:
https://www.corsair.com/eu/en/Categories/Products/Power-Supply-Units/hxi-series-2017-config/p/CP-9020140-EU

Would the existing cables that are connected to my current 850W PSU be able to be simply moved over to that one? So I could avoid having to redo the cable management in there. Or are the cables for a specific PSU, and you'd need to redo them.

And if anybody knows regarding my first two questions it would be a huge help (the extra 8-pin connections on a single cable vs 3 individual 8-pin cables / if certain 8-pin slots are dedicated to the CPU on the PSU, or if that's just down to the cable itself). Thanks!
 

Zerk2012

Titan
Ambassador
Thanks for letting me know!

In that case, if I were to upgrade to the following 1200W PSU for example:
https://www.corsair.com/eu/en/Categories/Products/Power-Supply-Units/hxi-series-2017-config/p/CP-9020140-EU

Would the existing cables that are connected to my current 850W PSU be able to be simply moved over to that one? So I could avoid having to redo the cable management in there. Or are the cables for a specific PSU, and you'd need to redo them.

And if anybody knows regarding my first two questions it would be a huge help (the extra 8-pin connections on a single cable vs 3 individual 8-pin cables / if certain 8-pin slots are dedicated to the CPU on the PSU, or if that's just down to the cable itself). Thanks!
When you switch power supplies always use the new cables.
For the other question yes if you only have 2 cables use both and it's OK to use both connectors on one cable.

Edit if you have your PSU manual it will probably say how many watts the single cable can handle using both connectors my Seasonic said either 225 or 250 watts been to long since I looked at it to remember what it was.
 
Last edited:
Jun 16, 2021
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When you switch power supplies always use the new cables.
For the other question yes if you only have 2 cables use both and it's OK to use both connectors on one cable.

Edit if you have your PSU manual it will probably say how many watts the single cable can handle using both connectors my Seasonic said either 225 or 250 watts been to long since I looked at it to remember what it was.
Great, thanks for all your help, much appreciated!
 

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