Ah that makes sense. How much power can be transferred through these adapters and the m.2 slot though? the other adapters i've seen have an extra plus for auxiliary power usually via 4 pin to SATA connector. Is it safe to use your adapter with a 1080 Ti? I read that 1080 Ti cards can pull 75 watts and over 4 amps through the PCI-E connector without an alternate power source.
My understanding is the pcie riser supplies the power the cards take through the pcie slot and no power traverses the USB cable. So no power should be pulled through the M.2 to GPU riser adapter.
Regarding the other m.2 to PCI-E 4x adapters, if your riser is powered then you usually don't need to plug power into the m.2 to pcie adapter. The power connection on a m.2 to PCI-E adapter is to power cards that would be plugged directly into the pcie slot on the adapter. In which case, you couldn't plug anything over pcie 4x anyway.
I just bought 2 of them for a couple 1080ti. I'll let you know if they catch fire.
Thats correct...these are designed for the GPU risers, and those are obviously self powered and don't pull power from the actual slot. Only thing that goes over the USB cable is PCIe data lines.