What is PCI-E?

PCI slots have been on motherboard for years, but some of you may have taken notice a newer trend in bus technology PCI-E. PCI Express slots are todays modern standard on most new motherboards and are blowing away older PCI standards and AGP graphic slots for speed. The new PCIe graphics cards are allowing higher speeds by utilizing 2 identical graphics cards placed in 2 identical PCIe slots. Brand names for this graphic solution include Nvidia's SLI, ATI's CrossFire. The new form factor can be confusing at first because unlike the old PCI slots PCI-E connectors are coming in X1, X4, X8, X16, X32.

Here are some more technically advance number on the PCI-E Revolution:
PCI 132 MBps
AGP 8X 2,100 MBps
PCI Express 1x 250 MBps
PCI Express 2x 500 MBps
PCI Express 4x 1000 MBps
PCI Express 8x 2000 MBps
PCI Express 16x 4000 MBps
PCI Express 32x 8000 MBps

It's worthwhile to note that any PCI-E card will work in a larger PCI-E slot. Meaning you can use a PCI Express 1x card in any PCI-E slot(2x, 4x, 8x, ect.)