FUD Zilla reports Intel's S4600LG "Lizard Head Pass" server motherboard can handle up to a terabyte of RAM:
After all 1024GB of RAM is not to be sniffed at and we should not really be worried about what a Lizard head's pass looks like. The board is designed mainly for high-performance computing and math-intensive server applications, such as video streaming sites using it for transcoding. We guess it could also be good at catching moths with its long tongue. If it is not passing of course.
Apparently the board can manage auch large memory expansion room by providing three DIMM slots per memory channel, with each socket giving four memory channels. The S4600LG supports the 8-core Xeon E5-4600 series Sandy Bridge-EP processors. The S4600LH is driven by an Intel C600 "Patsburg" chipset with up to 8 SCU ports and 2 SATA 6 Gb/s ports. One of the downsides is the board doesn't have any standard expansion slots, with only two PCI-Express 3.0 x48 risers, which daughterboards with three x16 slots each, can be attached.