Thanks to our generous funders, we purchased a 1-U rackmount server. It is a supermicro server with a 64-core AMD chip and 45TB zfs raid array. The primary use is hosting our PostGIS-enabled database. We wanted to train some neural networks and so purchased an NVIDIA 4090 GPU. The question is how to connect it to a 1-U server chasis. The solution I came up with is to run a PCIe cable out the back and attach the GPU externally with its own power supply. The blocker was that I did not know that the PSU will not power up without being plugged into a motherboard. In the end, I figured out that I could modify the provided CPU cable, crossing wires 16 to 17 and cutting short the rest, and then plugging this dongle-like remnant into the power supply. And viola! It worked. The other parts are a shelf for the rack and a stand for the GPU. I found the stand after a lot of web searching. I bought it off of Etsy and it was shipped from Turkey! You can see the result in the picture.