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PCI, PCI-e, AGP
PCI, PCI-X, PCIe, and mini PCI.
No, PCI Cards will not fit on PCI-E slots
Its either shorter than pci or longer than pci and agp
No, it's not. PCI-E 1x is compatible with PCI-E x4, x8, x16. PCI-E 4x is compatible with x8, x16 and so on.