PowerSave: A Tale of Two Products

I'm using two of several products launched in October. Windows 7, and

Amazon's Kindle 2 e-book reader, global edition. Both get a special mention in

this column on green tech.

You know by now that W7 is superior to its predecessor... of course. The less

said about Vista... W7 is faster. It installs quickly, starts and shuts

snappily, even loads apps faster. What surprised us, in our tests featured last

month, was performance on an old P4 PC with 1 GB memory. W7 ran faster than not

just Vista, but also faster than XP and two Linux strains.

Good software can also reduce power draw. Writing this on a ThinkPad T400

running W7, I notice that it uses the hard disk less. Other than quicker startup

and shutdown, there's less memory (and thus swapfile and disk) use...and less

CPU use. That translates into longer battery life. While I did not check this

out against Vista, a Microsoft-Intel test (http://bit.ly/W7-batt) on T400

laptops shows the W7 laptop drawing 15.6W, with 20% better battery life than the

Vista one (20.5W), playing a DVD movie-5.46 hours on W7 versus 4.14 hours on

Vista.

W7 smartly puts to sleep parts that aren't needed: a second CPU core, a hard

drive, USB ports, even Wi-Fi when you're not connected to a network. The system

timer's been tuned, and it also doesn't wake up an idle CPU unnecessarily,

reducing power draw further. W7 also lets developers more easily use resources

including the CPU on-demand, rather than running all processes all the time in

the background.

In its default setup, W7 may not be great on power efficiency. All those

smooth Aero and graphics effects draw power, use memory, and, together with

multiple apps loaded, can increase hard disk activity. Optimizing power and

extending battery life may need tuning: turn off Aero, minimize multiple loaded

apps when on battery, ensure your hard disk's de-fragged, and add RAM-2 GB works

better than 1. More on this after other tests in our labs.

On the Amazon Kindle, I'm midway through Dan Brown's Lost Symbol. The Kindle

is a quite delight, and it takes less than one book to get used to e-book

readers. But the real remarkable thing about it-and about other e-book readers

too-is power efficiency.

Battery life has to be a top feature on an e-book reader. You don't want to

be racing with the battery to finish a book, something you'd be doing if you

were using a PC or tablet with a five-hour battery.

So a big step for the e-book reader was e-ink, or e-paper. This display is

not backlit, but reflects light, rather like ordinary paper, so you can read it

outdoor too. It requires a little power only to update the display-and then it

stops drawing power.

So the Kindle runs for up to 14 days on a charge, with its wireless off. I

charged it for an hour out of the box and have now used it for five days so far,

with a bit of wireless use to download a book or two, and find the battery's

still showing nearly full.

The e-book reader is a great example of what advances in low power devices

and battery life can allow. Without the e-paper display and the long-life

battery, the Kindle and its ink would not have been possible.

The author is chief editor at CyberMedia, publisher of 15 specialty titles

including PCQuest.



You can reach him at pkr@cybermedia.co.in,
twitter.com/prasanto.