Western Digital (WD) is the first vendor to successfully create a piece Hard Drive with a capacity of 3 terabytes (TB), the largest capacity in its class. In contrast to the mode that is applied to the previous hard drive where each sector contains only 512 bytes of data. With Advanced Technology, a disk can have a greater amount up to 4.096-bytes per sector. This is what is claimed to make the WD Caviar Green 3TB more efficient.
The WD Caviar Green 2.5TB and 3TB drives have capacities in excess of 2.19 TB and this presents barriers for PC hardware, firmware and software. To get around these issues WD is bundling its WD Caviar Green 2.5 and 3 TB hard drives with an Advanced Host Controller Interface (AHCI)-compliant Host Bus Adapter (HBA), which will enable the operating system to use a known driver with correct support for large capacity drives. WD supplied us with a HighPoint RocketRaid 620 PCI Express 2.0 x 1 SATA III (6.0Gbps) controller card to use with the hard drive. (source : wdc.com)