SGI demoed a “concept machine” based around Intel’s Atom processor.  They put two dual-core Atoms in a cartridge called a “Molecule”, and built a 3U rack that can hold 180 cartridges.

180 carts x 2 cores = 360 cores

360 cores x 2 threads (hyperthreading) = 720 “virtual threads”

Oh, and it supports up to 720GB of memory, using normal DDR2 DIMMs.

All that in a 3U rack.

Wow.