A question to all the ones using server PSU... How do you power your pci-e x1 to usb risers? Do you use some kind of PCI-e 6 pin to 2xSATA extender? So, a server PSU with x8 PCI-e 6 pin connectors is not for 4GPUs, it is for 3 GPU plus risers..
I'm thinking into buying a really cheap refurbished FSP 500W ATX psu for mobo+cpu+16x GPU, and a server PSU for every GPU with a riser, But I can't see how to power risers only with server PSU without wasting so many connectors. PCI-e 6 pin are made for 150W max, aren't them? So for 75W max from PCI-e connector, that should be a PCI-e 6pin to 2xSATA for 2 risers.
Use PCIe risers that come with 6 pin connectors instead of molex/sata (they are availible now)
Use 1X2 PCIe power cables for the Server PSU, oir get PCIe power splitters, and use the two plugs per cable in GPU Power and Riser Power, thus powering One Card from one power slot.