Friday, June 13, 2008

Doubling Laptop Battery Life

Intel's new integrated power management could dramatically reduce power consumption in your laptop by shutting down operations not being used.

By Kate Greene

Anyone who uses a laptop on an airplane would love a single battery to last through a trans-American flight. Now researchers at Intel believe that they can double a laptop's battery life without changing the battery itself. Instead, they would optimize power management--system wide--of the operating system, screen, mouse, chips inside the motherboard, and devices attached to USB ports.

To be sure, manufacturers and researchers have been exploring piecemeal ways to make portable computers more energy efficient. Operating systems are designed to deploy power-saving screen savers and put an entire system to sleep if its owner hasn't used it after a while. And Intel's forthcoming Atom, a microprocessor for mobile Internet devices, can be put to sleep at up to six different levels, depending on the types of tasks that it needs to do.

But the problem with these approaches is that they're not coordinated across the entire device. Intel's prototype power-management system is aware of the power that's used by all parts of a laptop, as well as the power requirements of a person's activity, and it shuts down operations accordingly, says Greg Allison, business development manager. The project, called advanced platform power management, was demonstrated on Wednesday at an Intel event in Mountain View, CA.

Power bars: Intel Research engineers yesterday showed off prototype methods for system-wide laptop power savings. Using the current implementation, average power consumption of a laptop can be reduced from 6.23 to 4.02 watts. The researchers believe that the approach has the capacity to slash up to 50 percent of laptop power consumption.
Credit: Kate Greene

Allison gives this example: today, when a person reads a static e-mail, the screen still refreshes 60 times a second, and peripherals such as the keyboard, mouse, and USB devices drain battery power while awaiting instructions. "We're burning energy even when we don't need to," Allison says. In this situation, Intel's system would save power by essentially taking a snapshot of the screen that a person is reading and saving it to a buffer memory. So instead of refreshing, the screen would maintain an image until a person tapped a button on the keyboard or moved the mouse (the keyboard and mouse would also stay asleep until activated).

All the while, the operating system will be monitoring use of other applications, restricting operations to those that aren't being actively used. And if there are any devices plugged into a USB port, such as a flash-memory stick, the system would put them to sleep. At the same time, explains Allison, energy-monitoring circuits on Intel chips will put unnecessary parts of the microprocessor to sleep. It takes 50 milliseconds for the entire system to spring to life, he says, a length of time imperceptible to the user.

Intel isn't the first to think of the idea of integrating power-saving technology throughout a device. One Laptop per Child (OLPC), the nonprofit that builds inexpensive, rugged laptops meant for children in the developing world, set the standard with a gadget that consumes one-tenth of the power of a conventional laptop. Granted, OLPC's laptop doesn't have the capabilities of consumer machines, but it does show what is technically achievable.

There are definitely advantages to this systemic approach, says Seth Sanders, a professor of electrical engineering and computer science at the University of California, Berkeley. "Comprehensively looking through the system at all of the different pieces that are cycling unnecessarily provides an opportunity [for power savings]," he says.

Allison says that the company is already talking with operating-system vendors to explore what it would take to integrate this approach into software. And as a major contributor to the new USB 3.0 standards, Intel will have some say in how much power forthcoming USB devices will use. In addition, Allison says, the company is trying to secure deals with display and hardware vendors. "This won't happen in the next three years," he says. But he suspects that pieces of the new power-management system will find their way into laptops within five years.