Question: are all pci express slots the same?
Answer: PCIe slots come in different physical configurations: x1, x4, x8, x16, x32. ... Similarly, you can insert a PCIe x8 card into a PCIe x4 slot, but it'll only work with half the bandwidth compared to if it was in a PCIe x8 slot. Most GPUs require a PCIe x16 slot to operate at their full potential.