An X48 motherboard has two PCIX16 slots that actually are x16/x16. The one you chose is P45 which has 1x16 or x8/x8 when you run two video cards together.
An X48 can only be used with 2 ATI cards correct? SLI will not work on a X48 mobo correct? If so why? I never fully understood the Intel Chipsets.