GA-EP45-UD3P PCI-E Slots

I was just looking at the specs of my GA-EP45-UD3P on the website and i saw this :



1. 1 x PCI Express x16 slot, running at x16
2. 1 x PCI Express x16 slot, running at x8
(The PCIEx16 and PCIEx8 slots support ATI CrossFireX technology and conform to PCI Express 2.0 standard.)
3. 3 x PCI Express x1 slot
4. 2 x PCI slots



What does that bit in bold mean, why is it running at x8 even though its x16?
Since I plan on Crossfiring in the future what impact would that make if I'm running at 8x instead of x16?

PS: I will be using two 4870 1G vapor-Xs if that helps.

Thx mindless728, since it runs at x8 when I Crossfire that means both my cards will run at x8. Would that give me a performance blow compared to two cards that are running in 16x?