PCIe slots come in different lengths, corresponding to the amount of data they can move. PCIe x1 slots replace the standard PCI port and are about 1 inch (or 26mm) long. They move data on and off the motherboard at up to 250 MBps in each direction at once. The PCIe x16 slot that replaces the AGP graphics-card slot is 90mm (about 3.5 inches) long, just like a PCI slot. A PCIe x16 slot can move data--you guessed it--up to 16 times faster than an x1 slot can: as fast as 4 GBps in each direction simultaneously.