FBDIMM uses far fewer physical connections to the memory controller and that is its primary advantage. DDR2 really can't use more than 4 DIMMs because of the physical connections to the memory controller. Still using DDR2, FB-DIMM can manage dozens of DIMMs (48 or 96, can't remember). AMD has been addressing this issue by having a hive-mind kind of memory pool where every processor has its own dedicated DIMMs but the processors are capable of making memory requests with other processors. Intel wanted to avoid that and their answer to the problem was FB-DIMM. Yes, it has some performance and thermal drawbacks but when you need 192 GiB of RAM, you need 192 GiB of RAM.