Terabyte sized memory will soon be possible with Xeon (if not already), Amazon announced x1 instances with 2TB of RAM + 100 cores. They are using Xeon E7 CPU's:
that thing takes Xeon e5-26xx v3 CPUs which are pretty middle of the road server chips; Nothing fancy. If you want to go quad-socket with E7 xeons or something, you can get even more ram in one box, but the E5 Xeons are dramatically more economical than the E7 xeons.
I mean, the linked motherboard would be money, sure, but it would be the sort of cash that my company would be able to come up with.
http://www.supermicro.com/products/motherboard/Xeon/C600/X10...
that thing takes Xeon e5-26xx v3 CPUs which are pretty middle of the road server chips; Nothing fancy. If you want to go quad-socket with E7 xeons or something, you can get even more ram in one box, but the E5 Xeons are dramatically more economical than the E7 xeons.
I mean, the linked motherboard would be money, sure, but it would be the sort of cash that my company would be able to come up with.