On its path back into the black, AMD is going green. The company is putting a lot of weight on the new Opteron line in hopes of it revitalizing AMD's server business, and these new quad-cores promise 43% lower energy consumption.

Called the Opteron HE (for High Efficiency), these x86 Quad Core server processors have an integrated memory controller and a 55-watt ACP thermal envelope instead of the standard 95-watt profile.

These HE processors are available in both the 2300 and 8300 series for two-, four-, and eight-way rack and blade servers. Processor prices as of April 28 are posted on AMD's site.

What makes rational comparison a little difficult is that AMD uses a different metric for measuring power consumption than its competitors -- and even different from itself not long ago, so a fair judgment of the Opteron HE's efficiency is not so cut-and-dry. The 55W ACP refers to "Average CPU Power," or how much energy it takes to run the CPU, and the 95W figure AMD is comparing it to refers to the Thermal Design Point (TDP) metric, which is how much energy it takes to cool the chip.