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Low-Cost Tablet Runs on Three Watts of Power

Designed to teach math to students in poor countries, the device will be the first to use a new energy-efficient computing strategy.

After a year of testing in a remote village in India, researchers are ready to scale up production of an ultra-low-power $35 tablet called the I-slate.

Tablet power: Krishna Palem holds a prototype I-slate.

The I-slate is designed to teach math and other subjects to students whose schools lack electricity or to students who don’t have access to teachers at all. The device will enter full-scale production next year, and will be the first device to apply a low-power technology called probabilistic CMOS (complementary metal-oxide semiconductor) to achieve a longer battery life.

The probabilistic CMOS approach is simple: run an ordinary microchip less stringently, sacrifice a small amount of precision, and get huge gains in energy efficiency in return. Probabilistic CMOS (CMOS refers to the technology behind most of today’s chip technologies) works particularly well in graphics and sound processing, since human vision and hearing aren’t perfect, and small errors are therefore undetectable.

Krishna Palem, a professor at Rice University and director of the Institute for Sustainable Nanoelectronics at Nanyang Technological University, first demonstrated probabilistic CMOS in 2006. Palem is now working on getting the technology into applications including a low-power hearing aid. In the educational tablet device, Palem says, probabilistic chips will enable huge power savings: the educational tablet will require just three watts of power, meaning it can be powered entirely by small solar cells like those on a pocket calculator.

The I-slate looks similar to an iPad, with a seven-inch liquid-crystal touch screen display. But it’s not a full tablet computer—in fact, unlike other hardware supplied to disadvantaged children through efforts such as One Laptop Per Child, it’s not a computer at all, and does not have an operating system. “It’s an elaborate, single-function device,” says Palem. Kids can read from a preloaded textbook or take notes and work out math problems using a stylus on a “scratch pad” to one side of the screen. The device can store a few pages of notes.

Palem’s group at Nanyang Technological University is developing the I-slate in collaboration with the Indian nonprofit organization Villages for Development and Learning Foundation and the Los Angeles design firm Seso. Last year, the group tested prototype I-slates loaded up with a math textbook and exercises at a school in Mohd Hussainpalli, a village about 70 miles southwest of Hyderabad. In this region, electricity is unreliable, and some villages don’t have teachers.

Marc Mertens, the CEO of Seso, designed the I-slate interface. The challenge, he says, has been to figure out “what is the ideal way to work with students, while making sure the device does as little as it can.” That approach keeps hardware costs and power consumption low. Animations and other complex, media-rich tools are just not possible. The math program is based on the standard textbook used in the region and allows students to move at their own pace. They can skip problems if they get stuck. Teachers can download information from each student’s device to monitor their progress.

The field tests, which showed that the students’ math skills improved when they used the I-slate, were done using prototypes based on conventional chips. Next year, the researchers will begin producing the three-watt, solar-powered model.

“We keep chewing the hardware down, then evaluating the effectiveness of the interface and the lessons on it,” says Palem. “Once we are comfortable with the user interface, we will switch in the [probabilistic] chip.”

As Palem’s team works on upgrading the hardware, Mertens is working on broadening the curriculum that can be put on the I-slate. It’s much easier to design a program to grade math tests than written work, he says. “We’re exploring how this device could go beyond math and support more creative curricula,” he says.

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