Things got interesting the day Intel launched the Core Duo processor. Until then, it looked like a company obsessed with winning megahertz wars against AMD, IBM and Motorola rivals. But at least one company knew there’s more to making a great PC than having the fastest revving motor on the street.

With the Core Duo line of 2006, followed swiftly by Core 2 Duo, Intel laptops of sensible dimensions could see usable battery life of around 4 hours. The 2010 Core i-series updates upped the processing speed, but TDP figures of 25- and 35W were still ridiculously high for laptop life. As I’ve rambled on before, 12 hours should be the entry-point for all-day computing.

By all accounts it was Apple that kept pushing Intel to make sensibly frugal processors, to power its MacBook Air and future lightweight designs. Getting down TDP to 17W was a useful step in the past few generations of ?low-voltage Core chips. This season’s Core i5 du jour from the Haswell summer collection is listed at 15W. See Intel launches Haswell Core processor

More than that, it looks like Intel has tackled the problem of idle power suckage, letting an x86 chip take deep, deep slumbers between 15W chores. So, like the ARM chips that currently rule the world’s phones and tablets, Intel processors now stand a chance of being welcomed in mobile computing circles.

Which should please Intel’s old friend Microsoft, too, since its newfound mobile strategy has fallen on its face. Fewer people than it had hoped want power-sipping Windows RT on ARM - it’s pricey and capable of little useful functionality. And full-fat Windows 8 tablets couple bad value with appalling battery life, often 5 hours or less. That runtime was too short for comfort when Core first launched; today it’s just embarrassing.

Apple MacBook Air 13.3in (Mid-2013)

But, as our test of the 2013 MacBook Air suggests, Haswell finally puts Intel in the mobile game - and maybe even Microsoft with it. You can get as much work done with slower-clocked chips, and improved power dormancy means batteries lose almost nothing when you’re doing nothing.

Microsoft’s got its work cut out: IDC ranks its Surface Pro and RT sales in distant fifth position. That sounds almost promising but, combining all the devices Microsoft and every other Windows tablet maker have sold, sales figures total a tiny 3.7 percent.

Intel’s low-power arrival could even deflate the Microsoft tablet plan. Laptops in their new all-day guise may again edge out the rounding-error of Windows 8 tablet sales, as people realise just how much more you can do with a versatile always-charged laptop in comparison to a tablet suited to consumption.