Originally known as 3rd Generation I/O (3GIO), PCI Express, or PCIe, was approved on July 2002 as a serial computer expansion bus standard. PCI Express was designed as a high-speed replacement for the aging PCI and AGP standards and is available in different formats. The data transmitted over PCI Express is sent over wires (called lanes) in full duplex mode (both directions at the same time). Each lane is capable of transfer speeds around 250 MB/s and each slot can be scaled from 1 to 32 lanes. With 16 lanes, PCI Express supports a bandwidth of up to 4,000 MB/s. The following images show what the PCI Express slots look like on a motherboard.