Calxeda recognized that the cell phone industry had something to teach server vendors: how to save power.

The Austin, Texas-based startup yesterday said it has raised $55 million in venture funding round led by Vulcan Capital and Austin Ventures. It’s raised over $100 million to date and will use the new money to further invest in its ultra low-power server design.

Calxeda took on the problem of heavy energy use in data centers by turning to the ARM processor, a chip used in smart phones and tablets which are optimized for power efficiency. The company has made a system-on-a-chip that includes multi-core ARM processors and a dedicated chip for coordinating data networking between processors.

With its technology, a server can use as little as five watts and reduce its idle power to less than one watt. Tests show that its systems improve energy efficiency ten-fold over servers built with X86 processors from Intel or AMD, the company says.

Calxeda puts four of its EnergyCard systems-on-a-chip onto a single board. HP has built a server that packs 288 of these server boards into a 4U chassis. That means data center operators can put a lot of computing power in a relatively small space without causing heat problems from power. Those HP servers are expected to be available later this year.