I don't think the die size is a problem; AFAIK you can get very many pins out of a die, but getting them out of the package is where it gets expensive.
FB-DIMM is already a serial-style high-frequency interconnect, but it isn't needed on low-end systems.
I think this is really about business, not technology. What they want is not what the mainstream wants, so they must choose between cheap but memory starved systems or very expensive balanced systems. HPC people have been whining about killer micros for 20 years; this is just another version of it.
FB-DIMM is already a serial-style high-frequency interconnect, but it isn't needed on low-end systems.
I think this is really about business, not technology. What they want is not what the mainstream wants, so they must choose between cheap but memory starved systems or very expensive balanced systems. HPC people have been whining about killer micros for 20 years; this is just another version of it.