pcie x16 slot used for

A PCIe x8 card will fit in any PCIe x8 or PCIe x16 slot. PCIe cards larger than the PCIe slot may fit in the smaller slot but only if it is open-ended (i.e., it doesn't have a stopper at the end). In general, a larger PCI Express card or slot supports greater performance, assuming the two cards or slots you're comparing support the same PCIe ... nusa 88 slot