> A PCI Express card fits into a slot of its physical size or larger (with ×16 as the largest used), but may not fit into a smaller PCI Express slot; for example, a ×16 card may not fit into a ×4 or ×8 slot. Some slots use open-ended sockets to permit physically longer cards and negotiate the best available electrical and logical connection.
The number of lanes actually connected to a slot may also be less than the number supported by the physical slot size. An example is a ×16 slot that runs at ×4, which will accept any ×1, ×2, ×4, ×8 or ×16 card, but provides only four lanes. Its specifi…