ThunderX2 motherboards have 3 connectors for GPU power cables. The connectors are documented in the Gigabyte Server User Manual which can be found on their website, for example, User Manual. Chapter 4 illustrates the motherboard connections. In this case, the power ports are items 1, 2, and 14.
For space savings; Gigabyte chose to use a smaller power cable connector on the motherboard for the GPU power connection. In order to accommodate this; cabling is available to provide power to GPU or other end-point PCIe cards.
For cards which need a right-angle connector for space one each of 25CRI-150303-G5R is recommended per peripheral card power connector.
25CRI-350305-Y4R for Graphics Cards
25CRI-480300-Y4R for Graphics Cards
25CRI-860100-Y4R for GP GPU Cards
All the cables have same 8 pin motherboards connector.
For connection to the GPU, each have at least one 8-pin or an 6/8 pin connector similar to to the two below:
Below are pictures of 3 such cables and their part numbers: