Best use cases for a mismatched RTX 3090 (24GB) + RTX 3060 (12GB) setup?

Reddit r/LocalLLaMA / 4/19/2026

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The post asks whether a mismatched dual-GPU setup (RTX 3090 24GB on a primary fast PCIe slot and RTX 3060 12GB on a secondary slower PCIe slot) is practical for real workloads.
The author suspects that splitting a single large model across both GPUs would be a bad idea due to the PCIe bottleneck on the 3060, which could slow generation.
They want guidance on whether running distinct applications simultaneously on each card makes sense, versus using only the 3090 for everything.
Overall, the question is framed as seeking best-fit use cases for heterogeneous GPUs and how hardware topology affects performance decisions.

Hey everyone, I have a system with 32GB of system RAM and two GPUs:

RTX 3090 (24GB) in the primary fast PCIe slot

RTX 3060 (12GB) in a secondary, slower PCIe slot

I'm assuming that splitting a single large model across both cards is a bad idea because the slow PCIe slot on the 3060 will severely bottleneck the generation speed.

With that in mind, is this setup practical for running distinct applications simultaneously?. Or is it not worth the headache and I should just use the 3090 24GB for everything?

submitted by /u/chucrutcito
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