In 2018, I bought the Gigabyte B250 FinTech motherboard, in order to power my budding crypto-currency mining empire (the wisdom of this plan is yet-to-be-determined). The motherboard supports up to 12 GPUs, but the ordering of the PCIe slots seems to be semi-random. After struggling to correctly identify which of my cards were addressed by which PCIe slot, I painstakingly mapped out PCI address to the physical motherboard slot.
This is a companion discussion topic for the original entry at https://www.funkypenguin.co.nz/note/gigabyte-b250-fintech-pcie-slot-layout/