Question Hx1200 from Corsair Multi or single rail switch ?

Aug 8, 2022
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The switch came by default in multiple and I googled and saw that despite it having a switch, all modern PSUs are actually single-rail internally, despite the switch apparently limiting so no cable goes over 40.

The question is if I should set it to single since it is for a 3090ti, with an i9 12900k and DDR5 memory and board ?

Thank you.
 

Eximo

Titan
Ambassador
At 40 AMPs, probably not. That is 480W.

3090Ti will have spikes higher than that, but it depends on how quickly it acts on the OCP.

Depending on how you hook it up, you might have 80A total available for the PCIe power cables.
 

Vic 40

Titan
Ambassador
With the 3090 TI you should use three different pcie cables (single/first connector) which means you should draw power of more rails that way. No way all pcie /cpu connectors on the psu side are powered by one rail.
 
Aug 8, 2022
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At 40 AMPs, probably not. That is 480W.

3090Ti will have spikes higher than that, but it depends on how quickly it acts on the OCP.

Depending on how you hook it up, you might have 80A total available for the PCIe power cables.
Indeed, I will use individual cables, no daisy chain or anything.

I saw a few videos where some "builders" used adapters and it did not go well. I will plug 3 different connectors to the PSU to the 16 pin 3 connector adapter that the gpu comes with.
 
Aug 8, 2022
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With the 3090 TI you should use three different pcie cables (single/first connector) which means you should draw power of more rails that way. No way all pcie /cpu connectors on the psu side are powered by one rail.
Well actually some recommend place the switch in single to prevent any spikes. I have not change the multi position. It came that way. I will read a bit further because I would prefer to use multi, but I don't want it to turn off because the OCP triggers from normal behaviour.
 
Aug 8, 2022
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This EXACT question has been asked over and over again over the years, and has been thoroughly answered, by Jon Gerow (JonnyGuru) who is the chief engineer for power supply development at Corsair. Your answers can be found here:

http://www.jongerow.com/multiple-12V-rails/index.html
Thank you. I actually have read that. And watched that video and many others. But even here on tH forums some had opposite opinions.

I get internally most PSUs are single but this OCP will anyway trigger if more is drawn from the GPU. Ultimately my question is if leaving it in multi will not trigger the OCP during full workload on a 3090ti gamerock and instead I should set it to single for no OCP triggering.
 

Darkbreeze

Retired Mod
It doesn't matter about different opinions. There are two people whose opinions are paramount in this regard as they are among the most elite in the world when it comes to power supply design, operation and testing, and those are Jon Gerow (Chief engineer of power supply design for Corsair) and Aris Mpitziopoulos (Power supply reviewer for Tom's hardware, Techpowerup and Hardware busters as well as one of the founding members of Cybenetics). And you've read what Jon had to say about it, so, if there is anybody else who has a differing opinion on this I'd suggest that they apply for the job of chief engineer of power supply design at Corsair since they must know more than Jon does.

Also, there are two other considerations here as well.


Well actually some recommend place the switch in single to prevent any spikes.

One, the power supply doesn't cause spikes. The graphics card causes spikes. It doesn't matter whether it's a single rail or multiple rail power supply, that has absolutely ZERO bearing on whether there will be spikes or not. There are ALWAYS spikes that will occur. Some cards more or less than others but they all spike to some degree, which is why you want a power supply that is capable of handling said spikes but also capable of protecting itself if something outside spec occurs.

Which leads to the second consideration. Making sure you have a power supply with adequate capacity for the graphics card you are using and that is is one where all protections are tuned to where they are supposed to be. Since pretty much every manufacturer is recommending an 850-1000w power supply for 3090 ti cards, depending on exact model, I'd say your 1200w HX unit adequately assures that part.

As for the OCP, Aris seems to think OCP is tuned properly in his review for multi rail operation and since this is technically one of the better power supplies out there I don't really think you're going to have problems no matter which way you set it but like was suggested very early in this thread it's probably a good idea to simply try it. If you have problems with multi rail operation THEN switch to single rail. If you still have problems, then you don't have the right power supply and may need something with a platform that's a little newer but I doubt you are going to see issues unless you are manually overclocking something.
 

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