Re: Socket F, mcp55, mcp65 and drivers.
I cannot find it right now but when I looked this up in summer mcp55 was not supported at all. Apparently that changed by then. But I would hate to buy a SMP board, SMP CPUs and DDR2 registered memory (which fits no other modern platform) to try this in practice without confirmation.
Also, I think it's not a good thing NVidia doesn't even have a table of which mcp is in which chipset. It's no surprise that NVidia gets disrecommended in OpenSource circles.