USB 2.0 brought us 480Mb/s transfer speeds and 2.5 watts of power over the cable. This required either a second USB cable for additional power or a plug in power adapter. Either way, it was a hassle to power even moderately speedy external hard drives.
USB 3.0 brought a massive speed increase to 5Gb/s transfer speeds; however, power only received a relatively small bump to 4.5 watts of power over the cable (900mA at 5V). While the bump in power can now more easily power most external hard drives, power hungry high speed mechanical and solid state hard drives that are able to fully take advantage of the speed increases of USB 3.0 will still require additional power.
A USB powered flux capacitor.
In an interesting move by the USB 3.0 Promoters Group, a new USB 3 specification will provide up to 100 watts of power at varying voltages to external devices. This great increase in power would allow users to power external USB monitors without a separate power adapter, RAID enclosures, desk lamps, USB grills (okay, maybe not), and other multiple hard drive external enclosures like the Drobo boxes.
While the new specification is due out next year (2012), it will be some time before hardware (specifically power supplies) catches up to the specification’s maximum power draw. Do you think the move to deliver more power through the USB 3 cable is a good one, or will the increased complexity of delivering 100 watts over the same cable delivering data outweigh the convenience of only needing a single cable?