What speed, number of pins (physical size) are PCIe x1 x4 x8 and x16?
Normally I would google to find a photo showing the various types of PCI Express cards and their max bandwidth. Now that serverfault exists, I thought I'd lazily check if anyone here already has a good concise photo they could post as an answer.
EDIT: Thanks, vartec. I also found a nice diagram via Google: