AGP Motherboards vs PCI-e Motherboards
As with the previous AGP compatible motherboards, graphics cards are now designed to slot comfortably into a PCI-e motherboard. The problem is, to all but the very well trained eye, both slot types are identical, meaning that you need to be very careful which motherboard you purchase.
PCI-e graphics card slots (pictured, right) differ from standard PCI-e slots due to the available bandwidth (x16 as opposed to x1 and x4), meaning that while standard PCI-e cards can be placed in any suitable motherboard slot, PCI-e graphics cards can only be used in the appropriate slots (although some other PCI-e cards can be used in PCI-e graphics slots).
While dual-slot motherboards that offer both AGP and PCI-e graphics card compatibility are available, these are rare (and intended mainly for people who aren’t ready to upgrade their video card yet, as opposed to people who bought the wrong card!) so the chances of you finding or owning one of these is rare.
Note that for a more powerful graphics experience, PCI-e cards can be paired – ATI cards use the CrossFire technology, which requires two similar cards and two suitable (high-speed) PCI-e slots on your motherboard.
Checking the manual for your motherboard will help you to determine exactly what type of card you can use and in what configuration.