are all pcie power cables the same?
There are two ends to a power supply cable: The device-side and the PSU-side. The device-side of all PC cables is standardized. ATX 24-pin, EPS12V, PCI-e to the GPU, SATA—the wiring is known, and it doesn't change. What isn't standardized, however, is the layout of the PSU-side modular cable headers.