Why PCI Express backplanes are so expensiveunpopular?

It should be backward compatible, but you will see less performance than if you had it in a PCIe slot since it runs at PCIe x8 instead

#4 pci-e gpu are backwards compatible with pci-e slots, you might lose a few fps here and there but nothing to be concerned for

pcie slot qrelease With options for 1x, 2x, 4x, 8x, and 16x slot configurations, PCI Express doubles the speed of PCI Express , increasing performance from

pcie slot x16 PCIe Gen 3 x 1 PCI Slot x 3 30423052 B-Key x 1 (PCIe