Hypothetical question. 128 GB system RAM performance issues.

I'm planning a system based on the Sandybridge-E processor and noticed that MSI makes a MB that can support 128 GB of RAM. I also found 16GB sticks of registered server RAM that would work. No, I have no plans to make a system with that much memory. Right now I am planning a 4 x 8GB system. Still a massive amount of RAM, but more reasonable and it will fit in four of the eight slots in a quad channel configuration.

Anyway, it does leave me wondering... What would happen if I were to lose my mind and plunk down nearly $3400 for 8 16GB sticks? I believe that I've read that registered RAM is slower than unregistered and I know that filling all eight slots, regardless of the total amount of memory, will impede system performance. I'm curious what I would expect. Just exactly how is performance impeded? Would I notice a slow down in gaming?

WIth a single consumer desktop CPU, the "slowdown" would most likely first be from simply overtaxing the memory controller. Similar to running sticks in "1T" vs "2T". I'd really be curious to see it done, though. If the current (consumer i7) CPU's are actually capable of that much with a single chip. I know multi CPU servers don't have any issues.