The Caviar Green series' main angle is reducing hard drive power consumption - the obvious side benefits are cooler operation and lower noise levels. It does this with a balance of memory caching, lower spin and seek speeds - collectively known as 'Intellipower' - for power savings reportedly up to 40%. WD's Caviar Black series SATA II hard drives feature a faster spindle speed and 32MB of onboard cache. Drive capacities range from 500GB through to 1.0TB, but all the Caviar Black series drives use Perpendicular Magnetic Recording and dual processors (what doesn't these days?) to reduce CPU overhead.