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Centrino: lies, damned lies; and battery benchmarks

How is it possible that a chip maker can be hailed as having provided "a new dawn" for mobile users, when it has done nothing more than get battery life back to where it was two years ago?

Yesterday, we had the official birth of Centrino. It's a group of technologies designed to reduce the impact of faster processing on power consumption. With it, we've seen hype: "all-day computing" is one phrase you'll see. "Longer working battery life" is another.

Is it true? Well, not really, no, not unless you have believed battery life benchmarks in the past.

Now, it has always been a fact that the amount of power you get out of a computer is related to the power you push into it. Run the same chip faster, and it will get hotter. And the hotter the processor chip is, the more electricity it needs to maintain that temperature - which is just not what the mobile user wants.

Centrino is not just a brand name. It includes the old "Banias" processor, now called Pentium M, plus the new motherboard chip set called 855, and a wireless network stack on board, previously known as Calexico. And it's genuinely a breakthrough in one sense; it reverses a previous trend. That trend was for PC chips to use more and more power.

I've seen a genuine "all-day" computer. It was a demonstration of one of IBM's new ThinkPad notebooks. Instead of the standard battery, it has an "extended" battery with six cells instead of four. Instead of a CD drive, it has a drive-bay battery. And underneath, you can clamp the biggest battery of all, as a wedge-shaped platform raising the profile of the notebook by nearly an inch at the back.

All that, to get a genuine eight hours of life; and of course, it's heavy.

The problem is, there is no magic possible on this. In the past, Intel tried to fake "economic" portables with its speedstep technology. If the system detects the mains power has been pulled out, it slows the computer down. Well, yes; we always knew you could save energy by running slower!

How is it that Intel has been acclaimed for the new family?

Short answer: battery benchmarks tell lies.

The typical battery benchmark assumes that most of the time, the "user" of a notebook isn't actually using it. It assumes the disk will stop, and power down, and the display will go dark.

The result - as any notebook user will tell you - is that machines which come with a claimed three or three-and-a-half hour battery life, will almost just about get to two hours before telling you that you've done enough for the day. Either get to the mains, or switch off; and if you don't, it will switch off for you.

With the release of the Pentium 4 mobile family, things had got about as bad as they could get; and with Centrino, things are, roughly, back to where they were with the original Pentium III launch; the same weights of computer, and the same battery life.

It's welcome, of course. But if you get on a flight to the US, you'd better have a voltage converter and an expensive seat; or else, plan on catching up on some book-reading.

Do not imagine that you'll be able to watch a full-length movie on DVD. You will just end up wondering how it finishes.