Power Supply for two 850W 3090 GPUs?

I need to use two 3090's to be able to run multiple CUDA-based simulations simultaneously. In order to squeeze a bit more performance out of the system, I was planning on getting two Gigabyte AORUS GeForce RTX™ 3090 XTREME GPUs (their listed clock speed is 1860MHz, compared to the 1695MHz from the base GPU from NVidia itself).

I recently heard that SilverStone released a 1650W PSU that is capable of running two standard NVidia 3090s at the same time (https://www.extremetech.com/computing/315680-silve...  However, the listed power consumption of the Gigabyte version of the 3090s is 850W (compared to 650W from the base NVidia model).

I'm not too familiar with this whole PSU thing (I've only ever built one cheap, low-power PC before, so it's never really been much of a concern to me, especially since I was able to inherit a 700W power supply from my dad way back when), but I would imagine that the single power supply mentioned above would not be able to support both GPUs.  Am I correct in my assumption?

If so, the case that I am looking at can support up to two PSUs (although that would not be preferred, since the second PSU would start infringing on valuable HDD space). Regardless, would that maybe be worth looking into?

2 Answers

  • P
    Lv 7
    1 month ago
    Favorite Answer

    The problem is if you really start exceeding 1650W by much you will blow your typical residential breaker which at 15amps can only support about 1800w.  Keep in mind you also need extra power for things like the monitor, light, and anything else you share that circuit with.  The good news is the cards probably use significantly less than 850w most of the time.   Additionally the "suggested" power supply sizes for the video cards include the power needed for everything else in the typical computer.  This means that the second card doesn't actually need an additional 850w.  A second 3090 only needs about 400w of power.  


     Two power supplies are definitely an option and it would allow you to run an extension cord to another circuit in the house.    I wouldn't worry  about physical space to put the hard drives since no one uses the larger 3.5 inch drives anymore and most people are getting the m.2 NVME PCIe SSD's which don't even go in the bay areas.    They make server cases specialized for multiple power supplies so you could always consider those. 

  • 1 month ago

    while you're pondering this, search the internet to see if and how two PSUs can exist in the same box.  It might not be as simple as you'd like to think.  I recall that, some years ago, special auxiliary PSUs were made to add to a standard PSU to increase power output -- the one I remember fit into the 3.5 inch HDD slots.  No idea if these are still a thing ... haven't considered such a possible need in well over a decade.

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