What sorta level of card are we looking at before x4 2.0 become a problem, 2GB/s bandwith doesn't seem terrible, will this stop a 4770 CF from properly functioning
shouldn't be a problem, it's only 4770, they've tested crossfire 5870, and at x4 2.0 it's still acceptable (within 10% performance loss)
Legion Hardware have done some testing on PCI-E bandwidth on Intel boards and 4850s. The results are interesting. The 16/4 arrangement of PCI-E lanes did not perform as well as the 8/8. Interestingly enough the performance of the PCI-E 1 and PCI-E 2 boards was not particularly different. To me that indicates that the available bandwith is not as important as how the PCI-E lanes are connected to the processor. I am assuming the 16/4 use 4 PCI-E lanes off the southbridge and the DMI connection is probably the bottleneck. Without knowing what resolution you are running and the configuration of the board you are using it is hard to say definitively that using a 4 lane PCI-E slot would not be a bottleneck. However I do think that 2 4770s in crossfire would still perform better than a single 4770.
