Facebook claimed Thursday to have manufactured a more energy-conserving server for its new data center than either its predecessor data center or the servers typically constructed by mainstream server suppliers.

At a time when the clients accessing the cloud seem to be in a race to be the smallest, there's another contest going on -- to build huge data centers that use the least energy. Facebook, by publishing its server specs at OpenCompute.org, illustrated both that it had borrowed key design principles from its predecessors, while at the same time advancing the state of the art.

The result may be an ongoing arms race among the biggest companies on the Web -- Facebook, Google, Amazon.com -- to build not only the biggest but also the most efficient data centers on earth.

Facebook's Mark Zuckerberg, for example, said his firm's new Prineville, Ore., data center had achieved a power usage ratio of 1.07. (The ratio is a standard measure of compute power gained for electricity consumed, called power usage effectiveness.) Google said state of the art is a ratio of 1.2, but it's been able to achieve 1.1 in one of its centers. There's some one-upmanship evident in Facebook's announcement, at a time when Google is explicitly saying it wants to compete.

Facebook VP of technical operations Jonathan Heiliger said at an event at the Palo Alto headquarters Thursday that the new servers are 38% more energy efficient than their predecessors. Part of the gain is a result of a redesign of the data center power system itself. Facebook brings in power off the grid at a pressure of 480 volts, compared to 120-volt household current. Electrical energy is lost at each step of the distribution process from power plant to consumer due to resistance in the lines and the inevitable generation of heat as transformers step it down to useable current.

Facebook somehow found a way to execute the step-down process in a more efficient way in its new central Oregon data center.

At the same time, it feeds power to servers equipped with power-sipping motherboards of its own design. Some of the components found on a standard PC motherboard are stripped off the Facebook motherboard design. At its heart is an 85-watt, AMD dual socket Opteron 6100 or Intel Xeon processor. The design supports six disk drives and up to four fans.