Seagate’s latest external hard drive has come up with a curious solution to the issue of USB 3.0 upgrades – put the interface on the cable rather than the drive.

This means that the new 2.5 inch GoFlex Ultra Portable drives are neither USB 2.0 or USB 3.0, and come with a port into which an interface is plugged. This can be FireWire, eSATA, USB 2.0 and, importantly USB 3.0, which allows the user to choose a lower spec before upgrading to USB 3.0’s better performance if that is desired at a later point.

Actually using the drive with the USB 3.0 will also require that the PC or laptop has a USB 3.0 interface. Seagate has also announced desktop and laptop adaptors to achieve this.

The basic square drive itself comes in 320GB, 500GB, 750GB and now 1TB capacities, costing $89.99 (approx £60), $119.99, $159.99, and $199.99 respectively, which includes a USB 2.0 interface kit. Getting the USB 3.0 interface, attached cable and laptop adaptor adds another $79.99 (approx £53). The desktop PCI adaptor costs $39.

Critics will point out that a more conventional approach would be less confusing – just buy a USB drive with the new interface built in and pay a bit more. Seagate’s approach might appeal to buyers who don’t want to make that investment yet but want some future-proofing.

Seagate’s design also adds cost. Getting a 320GB USB drive with all the necessary add-ons will set users back $170, a considerable premium over today’s USB 2.0 designs and possibly more than just announcing a conventional external USB 3.0 drive.

Seagate also introduced other external drives using the same design, including the GoFlex Pro, which features continuous backup and integrated 256-bit AES encryption. This also allows the user to choose USB 2.0 or USB 3.0.