A standard 4U rackmount enclosure measures 7" tall, 19" wide, and up to 24" deep. How many servers do you think you could cram in one of those? 20? 100? How about 288? That's the maximum density of Gemini, a high-density server spawned by HP's Project Moonshot initiative.
Each one of the "server cartridges" contains a server-optimized Intel Atom processor code-named Centerton. The 64-bit chip has hardware virtualization support and takes advantage of ECC memory, making it well-suited to enterprise environments. Although Centerton isn't listed on Intel's site, the new Atom was discussed at IDF Beijing last month. It reportedly has dual cores and a 6W thermal envelope. 32-nm fabrication technology is used to build the chip.
Project Moonshot aims to reduce server complexity, which seems contrary to packing more processors into a rack. HP's approach here is pretty straightforward: "move from tens of servers per rack that share basically nothing to thousands of servers per rack that share almost everything." Each Gemini cartridge features an Atom SoC, independent memory, and either direct or network-attached storage—that's it. The chassis' cooling, power, networking, storage, and management resources are all shared by the cartridges within.
According to HP, there's considerable potential for energy, cost, and space savings. Even cabling is reduced. I'd expect the server cartridges to be easy to replace, as well.
If this sort of high-density server tech sounds familiar, that's because it's similar to the interconnect fabric developed by SeaMicro. AMD bought SeaMicro back in February, and at the time, it promised Opteron-based solutions in the second half of this year. The next logical step is micro-servers based on processors derived from AMD's low-power Brazos platform.