One of the oddities of computing is that even though your computer is never fast enough, the CPU spends most of it’s time hanging around waiting for something to happen.

That presents a problem because the CPU is then wasting power so there are all kinds of clever tricks for slowing them down or reducing the voltage to save electricity. You might think this is only of interest to notebook users, but remember that this could have a reasonable impact on your electricity bill.

Following a tip from a reader (thanks Ashley), I did a bit of digging into the power plans on Windows Vista. I have to admit that I’ve never really paid that much attention apart from making sure that Power Saving is selected when I’m running off batteries.

What I discovered was the difference between the Full and Balanced power schemes. I’d flitted between them but hadn’t noticed any difference.

It turns out that Balanced mode scales the CPU speed (or frequency) depending on how busy it is. If there is nothing going on it runs at half speed and gets progressively faster as the work load increases. It’s impressively dynamic, compared to the slow/fast that I’ve seen in Ubuntu with the CPU frequency utility.

There’s some interesting analysis over at The Metaverse showing how the CPU frequency is automatically throttled in Balanced mode. But I decided to do some of my own.

There’s a lot of boring figures but the upshot is that in the PC Mark tests we ran there was no performance drop when using Balanced over Full Performance.

Given that power consumption should be reduced with the CPU speed reduction, I’m struggling to think of when Full Performance would be a good idea.

At last, a way of being green with no drawbacks!