Western Digital's claims to have cut the time to back up data to an external drive from one hour to just 12 minutes.

The company's eSATA-connected My Book Premium ES Edition is a serial ATA (SATA) drive than can connect to a PC host via an external SATA (eSATA) connection This is the same speed as the SATA interconnect used inside servers and PCs with internal SATA drives. It transfers data at 300MB/s. In comparison USB 2.0 transfers data at 60MB/s. It also obviates the need for ATA data signals to be translated into the USB protocol and back.

USB predates SATA drives and it use was to remove the cable clutter at the rear of PCs by replacing the various different cable types with just one interconnect, hence the 'universal' serial bus. However, it now connects everything from slow speed devices like mice to faster external disk drives. As these drives have reached 500GB capacity and beyond and been produced in the SATA format they have been pressed into service as backup devices. The USB interconnect is too slow for this function with a 20GB backup taking 100 minutes or more. Consequently drive and motherboard suppliers are producing an extension of the SATA interface to connect external SATA drives to the PC and reduce such a backup time significantly.

Virtually all motherboards shipped today include the SATA interface for internal drives and many PCI cards are available to connect eSATA hard drives to PCs and Macs. An increasing number of motherboard manufacturers are incorporating support for eSATA connector ports. In the absence of an eSATA socket on the back of a PC an PCI card is needed inside the PC to provide such a socket and then a short cable can connect the eSATA drive to this socket.

La Cie sells a 150MB/sec card for $50, around £30.00. MRI sells a SATA 2 card. Iomega includes an eSATA PCI card with its 500GB eSATA drive - £146.27 inc. VAT. Western Digital joins Seagate, La Cie and Iomega in making eSATA external drives available. Addonics has an $80 (about £50) Cardbus device providing two eSATA interfaces for notebook computers.

If eSATA does become popular then we can expect both desktop and notebook PCs to come ready-fitted with eSATA ports.

Western Digital's My Book Premium ES is now available at an estimated price of $179 (around £100) for 320GB capacity.