How Altera Cyclone IV GX PCIE work as PCIe x2 and x4?

Hi,

I am using PCIe with Cyclone IV GX now,and i am in confuse.

As we know,C4GX has one PCIE hard ip core,and it can configure as PCIE x1,x2,x4,
and my question is: how PCIE x2,x4 works? because the hard ip only provide one Avalon-ST data interface for the RX/TX. if i configure it as PCIE x2/x4,it also only one Avalon-ST data interface there. i also read the spce of the ip. x1 can work at 125M@64bits or 62.5M@64bits, x2 works at 125M@64bits , x4 works at 125M@64bits, so only this frequency, how to achieve 850MB/s when work at PCIE x4 Gen1?

can anybody explain to me? i am very confused...


Rgds,
stephua.