pcie 3.0 on 4.0 slot: How To Check PCIe Slot Version, Generation & Bandwidth. Can I Use a PCIe 4.0 Graphics Card in a PCIe 3.0 Slot? - TechReviewer. PowerColor Readies Single-Slot, 4-way CrossFireX Ready HD 6850 ... .
PCIe slots feature the same pin layout and thus are forwards and backward-compatible. However, a PCIe 4.0 card slotted into a PCIe 3.0
slot will run at the lowest denomination speed (PCIe 3.0).
5x PCI-E x16 slot PCI_E1 Gen PCIe 4.0 supports up to x16 (From CPU) PCI_E2 Gen PCIe 3.0 supports up to x1 (From Chipset) PCI_E3 Gen PCIe 4.0 supports up to x4 ...
If you buy a PCIe 4.0 expansion card but only have PCIe 3.0
slots on your motherboard. You can still use PCIe 4.0 expansion cards with PCIe 3.0 motherboards, thanks to PCIe 4.0’s backward compatibility.