How Single PCI slot running multiple GPU's

Pci and Pci-e slots explained pci 1 slot PCIe outperforms all other types of PCI expansion slots Table shows different PCIe versions TABLE PCIe versions PCIe version Speed ( pcie x4 in x16 slot For example, my NIC is a ConnectX3 single port which is a x4 card That's not going to fit in a 1x slot

pcie slot length What is it and how can I use it? (With 1-slot GPUs, other connectors are visible, including one which is probably the old PCI connection