The cheapest of the SpeedStep machines we've looked at is Rock's Sigma, which combines a 600MHz PIII SpeedStep processor with a sensible 128MB of SDRAM and a mid-size 6GB Toshiba hard disk. The spec is fleshed out by a 6-speed Pioneer DVD-ROM drive, and you get an internal Lucent V.90 fax modem as standard, which is always a worthwhile feature on a portable.

The Sigma weighs 3.35kg, which is about right for a three-spindle notebook, but we did notice a degree of flex in the case body which suggested that better design and thicker mouldings might not have gone amiss here. That said, the plastic lid surface did resist pressure pretty well, and should protect the screen from damage when the machine is closed for transport.

The screen itself is a 14-inch TFT panel running at the now-usual 1024 x 768 XGA resolution, and while it would have benefitted from slightly brighter backlighting, it was otherwise fine. We also quite liked the keyboard, which wasn't cramped and had the advantage of decently large keys where they are needed, specifically the Spacebar and the Enter and Backspace keys.

Performance was fine for a PIII/600, with the 128MB of memory and a reasonable 8MB ATI Rage Pro LT graphics chipset helping things along, and as we've said, even the 600MHz SpeedStep is breaking new ground relative to previous notebook processors when it comes to performance.

We were less happy about battery life though, which proved to be the Sigma's weak spot. Everything went dark after a little less than two hours, and we're really looking for rather more than that in our ideal notebook.

Despite the battery life, if you want a notebook at home or in the office rather than out on the road, the Rock is one of the most affordable SpeedSteps around at the moment.

Rock - Sigma 600 DVD price

£1,599 + VAT