I have found a few controllers that are OEM LSI MegaRAID 320-2E, and they do support PCI Express 2.5 GHz x8 link for 2 GB/sec peak simplex or 4 GB/sec peak dual simplex bandwidth. I'm not sure if it is compatibe with xp (looking for specification of it now).



(only have one 16x PCIe in my asshat Dell Dimension at work)