what is a PCI Express x16 MEAN...ThanksPCI Express, officially abbreviated as PCIe (and sometimes confused with PCI Extended, which is officially abbreviated as PCI-X), is a computer expansion card interface format. It was designed as a much faster interface to replace PCI, PCI-X, and AGP interfaces for computer expansion cards and graphics cards. The PCI Express (PCIe) physical connection (slot) is completely different from those of the older standard PCI slots or those for PCI Extended (PCI-X).

PCIe is based AROUND serial links called lanes. With PCIe 1.1 (currently the most common version) each lane carries 250 MB/s in each direction. The connection between card and motherboard consists of between one and 32 lanes giving a maximum transfer rate of 8 GB/s in each direction. Lane counts are generally referred to with an x prefix so for example x16 is shorthand for 16 lane. To put the speed into perspective, a single lane has nearly twice the data rate of normal PCI, a four lane slot has a comparable data rate to the FASTEST version of PCI-X 1.0, and an eight lane slot has a data rate comparable to the fastest version of AGP.

PCIe slots come in a variety of sizes referred to by the maximum lane count they support. A larger card will not FIT in a smaller slot but a smaller card can be used in a larger slot. The NUMBER of lanes actually connected may be smaller than the number supported by the slot size. While a 16 lane card cannot be used in an 8 lane slot it can be used in a 16 lane slot with only 8 lanes connected.