P55 and shared PCI-E

Hi

I don't understand that point :

On most P55 motherboard, you find 2 PCI-E x16 slot

when used with 2 Graphics cards, you run at x8/x8 on each slot

what's appening if you have only one graphic card and one PCI-E device is pluged on the 8xPCI-E slot ?


for example, you get this : http://usa.asus.com/product.aspx?P_ID=lGYmelQ8mJvPtYTv&templete=2
this device need Hi bandwidth , at least PCI-E x4

so is your system running at 8x/8x or 12x/4x ?
(the device takes what he needs or the motherboard share the PCI-E x16 in x8/x8, with no regards of the device's bandwidth connected?)

you can do the same with a PCIE x1 device pluged on 8x PCI Device
do you have a system running et x15/x1 or x8/x8 anyway?
( so the graphics card is limited and the device has more bandwidth he needs)


thanks for answers or sorry for english mistakes, it's not my native language