Wrapping up Speeds and Feeds, part 1: Efficiency

Laptop battery life is increasing steadily, but what we really need is for laptops to work like cell phones: always on, always running, and able to stay awake longer than we do. It is possible.

After 19 months of consulting--in Silicon Valley, we prefer that term to "unemployment"--I've accepted a job.

Once I start, I'll have to stop blogging. But while I'm still independent, I'd like to wrap up here by offering a short series of articles addressing several key topics in the area of personal computing.

Today, the topic is energy efficiency.

Energy efficiency has become a major selling point of today's personal computers, especially laptops, because power consumption determines battery life.

Unfortunately, laptops are being optimized for energy efficiency in a way that isn't fully consistent with the needs of laptop users.

Advances in process technology and CPU design have greatly improved the power efficiency of modern microprocessors when they're running. This improvement is most visible at the highest performance levels.

Over the last few years, dual-core laptop processors have gone from maximum speeds of roughly 2.4GHz to 3.0GHz without consuming any more power. The newest quad-core chips provide much more aggregate performance in a similar power envelope.

This improvement in operating efficiency is great for gaming, mobile video editing, and a few other applications. But it's not very meaningful for most consumers.

What the rest of us need is non-operating efficiency, the ability of the laptop to consume very little power when it isn't doing much because that's what our laptops are usually doing.

We need laptops that can do nothing--more efficiently.

I've been looking at the newest crop of ultra low-power laptops. Based on published benchmark data, they consume an average of 8W to 10W of power when doing essentially nothing (what we call "idle power"). Even the best of them consumes about 6W of power at all times, getting 10 hours of battery life from a 60WH battery. Maybe 2W of that is spent keeping the display on. The other 4W to 8W is just wasted by the CPU and other motherboard circuitry.

When your laptop isn't doing much--for example, when you're typing in your word processor--it's using only slightly more CPU performance than your cell phone is when you're texting. Your cell phone consumes very little power to do this meager amount of work, usually no more than 0.25W or so for the CPU and its support chips. The corresponding elements of your laptop, however, may consume 50 times as much power under similar conditions.

Some of this difference is inevitable; your laptop has wider data buses, more and faster RAM, and so on. Nevertheless, your laptop motherboard could be designed to idle along on 1W or so.

That would give you a total system-level power consumption of around 3W--half the power of today's most energy-efficient laptops and about one-quarter the power of an average machine. Because there's a relationship between peak CPU speed and idle power, today's fastest laptops consume 20W or more at idle. With more energy-aware designs, these systems could see even greater proportional reductions.

In other words, adopting more aggressive methods for reducing idle power could easily double battery life across the board, and some systems would see much bigger improvements.

This is not merely a quantitative improvement. Consider what happens when your laptop can comfortably operate for 20 hours with the display on, or 60 hours with the display off.

For one thing, it never has to go to sleep. Your cell phone never really goes to sleep, and that's a great part of its value. Your laptop can have this same cell phone operating model.

Closing the lid should turn off the display, but the machine should keep running. It can stay connected to the Internet over Wi-Fi or 3G, periodically download your new e-mail messages, watch that eBay auction, and do whatever else you need it to do...all the time. Just plug it in to recharge while you're asleep. (If the laptop is in your briefcase, it'll have to slow down a lot to keep from consuming too much power, but that's easily managed.)

When you're ready to start using the machine actively again, it shouldn't take any longer to turn the display on again than it does to physically open the lid. Think "always on," not "instant on."

All of this is possible with today's technology, but nobody's doing it. I think one of the reasons we don't see this usage model is that laptop buyers don't know to ask for it. Incremental improvements produce adequate sales figures with each new laptop generation, and everyone figures that's good enough.

But mark my words: the first full-function laptop that works like a cell phone--always running, always connected, always ready--is going to hit the market like a sledgehammer. Everything else is going to seem obsolete overnight.

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