Need help with the logistics of two BIG 3090s in the same case.

Reddit r/LocalLLaMA / 3/30/2026

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The post asks for advice on how to physically install two NVIDIA RTX 3090 GPUs (“BIG 3090s”) into a single home server case where one card partially blocks the other’s PCIe slot.
The author proposes three mounting approaches: placing the second card in the lowest available slot using an 180° PCIe riser, relocating the PSU to improve airflow, or using a vertical mount for the second card.
They plan to power-limit both GPUs to 220W, making cooling and airflow management central to the decision.
Options 2/3 require mounting the PSU at the bottom of the case and using a short extension cord, and the author requests safe, practical suggestions for securing the PSU in that position.
The discussion is framed as hands-on hardware/logistics problem-solving for a multi-GPU setup commonly used for local inference/training workflows.

Need help with the logistics of two BIG 3090s in the same case.

Yes… I should have planned better 😅

What is my best option to mount 2x BIG 3090s into the same home server case when the first card is partially obscuring the second/bifurcated pci-express slot? Both cards will be power limited to 220W.

I see three possible solutions.

Option 1. Mount the second 3090 in the lowest possible position, below the motherboard, about a half inch above the top of the power supply. Use 180° riser cable to loop back above the motherboard and into the PCI express slot. Airflow to 1/3 fans is somewhat restricted.

Option 2. Same as 1 but I move the power supply to the front of the case, providing more airflow to the second card.

Option 3. Same as 2, but use a vertical mount to secure the second card to the case. Potentially getting better airflow?

Option 2/3 requires finding a way to mount the flipped power supply to the bottom of the case, then running a short extension cord to the back of the case. Is it’s worth it? If so, please send suggestions for how to secure a power supply to the bottom of the case safely.

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