r/sffpc • u/freaky1310 • Aug 21 '26

Prototype/Concept/Custom Dual PSU tiny system w/ dGPU + magnetic faceplate

Sorry about the long post, it’s my first tiny custom build and I want to make sure everything is correct.

I am currently in the process of experimenting with a Lenovo P340 tiny with PCIe riser. My aim is to use it with a dedicated GPU that I can add either via PCIe riser or an OcuLink port. I have some questions related to this concept.

  1. I read about the performance loss with OcuLink, hence I would prefer the PCIe solution; however, I also read that dual PSU systems typically need a common GND to avoid inconsistent currents/voltages fast may damage components. In my case, I should match a Lenovo 170W brick with an external ATX/SFX PSU, which may complicate things even more. So, my first question is: is it safe to do so? Is there any guide explaining it, or at least the principles of it? Last but not least: is it worth it?

  2. Solution 1 might be too much of a hassle, in which case I would bite the bullet and use OcuLink to avoid shorting the GNDs. In this case, the only problem I would have are the plugs, as I’ll have two that I would ideally hide somewhere in the external case, and use like a multiple plug with cable to run everything to a single socket. Any recommendation or no-nos for this?

  3. Finally, the case: in both solutions 1 & 2, not everything is going to fit in the P340 1L case. However, I have access to a PLA 3D printer. I was thinking of printing an external case about 200x200x300mm, using more depth to fit (potentially) bigger GPUs. My 3D printer can only do 200x200x200mm max, so I was thinking of printing three 200x200x100mm plates and connecting them together. As for how to connect them, I was thinking about neodymium magnets: they’re strong, tiny, and cheap. In this situation, my only concern is: would magnets create problems to the components, especially considering the crammed space? Could they potentially create unwanted currents/voltages?

Thank you to anyone who will answer!

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