> the expansion bus of the 970MP has a LOT of PCI-E lanes.
The PPC970MP provides no PCIe at all, but connects via Elastic Interface to the IBM CPC945 (aka Apple "U4"), which in turn connects via HyperTransport to the ServerWorks HT-2000 (aka Broadcom BCM5780). The 16 lanes for the x16 slot are provided by the CPC945/U4, while the other 16 lanes for the x8 slot and the two x4 slots are provided by the HT-2000/BCM5780.