Powerful PCs don't have to be power-hungry, claimed OQO this week as it launched a Windows Vista-capable version of its 02 ultra-mobile PC (UMPC), sporting VIA's latest ultra-low-voltage (ULV) 1.6GHz processor chip.

The pocket-sized device can be used as a tablet PC, or else a backlit keyboard slides out from underneath the 800 by 480 pixel wide-VGA screen. It weighs just under 1lb (450g), measures 142 by 84 by 25mm, and can run for up to three hours on its 4500mAh battery, said OQO.

That's perhaps a tenth of the battery capacity of a conventional laptop, and it suggests that the device consumes on average just a few watts. Some of that can be accounted for by the VIA C7-M ULV processor, which is fully Intel x86-compatible yet has a maximum thermal design power (max TDP) of just 7.5W, and typically runs on far less.

Increasingly though most of the power consumption in portable PCs is elsewhere - in particular the screen and its backlight, and the memory. The 02 saves on the former, having a 5-inch TFT with less than a quarter of the surface area of a typical subnotebook's screen, but for Vista-capability it still needs 1GB of RAM.

It also has a hard disk - 80GB in standard models, but with 120GB drives and 32GB solid-state disks available as options.

The OQO 02 is sold in the UK through Expansys. Based on US pricing, it looks likely that the new 1.6GHz version, with XP Pro or Vista Business, 1GB RAM and an 80GB hard disk, will list here for around £1100 plus VAT.