PCI Express, which is abbreviated officially with PCIe (also PCI-E is often used) and should not be mistaken for PCI-X, is an implementation of the PCI connection standard that uses existing PCI programming concepts, but bases it on a completely different and much faster full duplex, multi-lane, point to point serial physical-layer communications protocol. PCI Express was formerly known as Arapaho or 3GIO for 3rd Generation I/O. PCIe transfers data at 250 MB/s per lane. With a maximum of 32 lanes, PCIe allows for a total combined transfer rate of 8 GB/s. To put these figures 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, and an eight lane slot has a data rate comparable to the fastest version of AGP. The full duplex point to point nature of PCIe should further improve its advantage over PCI, particularly in systems with many devices.