You may have noticed that if you really put your smartphone through its paces, probably by playing a complex 3-D game on it or running a GPS navigation app while also listening to music, that bits of its case get weirdly hot. This is thanks to the immutable laws of physics: Moving electricity around generates heat. Also the electronics inside a phone are jammed into a tiny space and there's not much room for the traditional cooling solutions used in laptops and PCs.
Mobile chips are actually optimized so they don't waste energy as heat and thus make your phone case melt or, more crucially, burn too much precious battery power. They use a number of tricks for this purpose, including strict power management via underclocking against their full potential clock speed. They are also sectioned up into task-specialized silicon, so that parts of the chip can go dark when they're not needed and only the light, and thus hot, bits are busy making a call or calculating the math for 3-D graphics.
Ideally to make a more powerful device, phone designers would like to cram more transistors into a tighter space and run the overall chips faster—and that's exactly the sort of progression that Apple's followed with each generation of its iPhone-powering Ax series of chips. It's a mini, mobile Moore's Law...if you like. But to do this is a difficult task, as the push to make a device more powerful has to be balanced against the need to keep the battery life meaningful and also the thermal properties of the circuitry and the phone casing.
Which is where, as Wired reports, the University of Michigan's innovation comes in. A team there has reimagined two aspects of mobile chip design: Cooling and chip power management.
The cooling aspect is rather remarkable. Instead of opting for merely letting the chip's packaging and the overall chassis of a phone act as a heatsink for a mobile chip, as happens typically now, they've covered the surface of a mobile chip with an ultrafine metal mesh. The metal, of course, has excellent thermal properties that carry heat away from the surface of the silicon and help it achieve more power efficiency. But they've filled the pores of this mesh with a high temperature wax-like material that acts as a second heat sink. When the chip overheats past a critical temperature as it's put to complex tasks, the excess heat energy is dumped into the wax...which absorbs the heat then melts. The wax material is actually a blend of paraffin wax and aluminium foam, together making what's called a phase change material.
Secondly instead of adopting a power management regime for mobile chips that switches portions of the chip off, the team has been testing "computation sprinting." It's a system where instead of causing chips to overheat by running them at full power for an extended period, the computer power is instead pulsed. In this model the chip effectively sprints, heats up, then jogs and cools down before sprinting again. The wax material can absorb way more energy than simple air cooling would allow, boosting chip operations enough that where a "sprint" profile would overheat a typical chip in just 20 seconds, the wax-cooled chip could manage to sprint for 120 seconds continuously.
In experiments with an Intel Core i7 chip that runs comfortably at a 10-watt power level, they've managed to "sprint" it up to 50 watts without overheating beneath the wax layer. That offers a significant computational power boost, and it's less than the 100 watts they're confident they can achieve.
These two technologies have amazing promise in the mobile world, when they're commercialized over the next five years or so. Your current generation smartphone is probably about as powerful as a typical desktop computer of about 10 years ago, and imagine what this power-boosting system could manage alongside the more traditional improvements in mobile chip design.
Mobile chips are already about to undergo a dramatic paradigm shift with the innovation of FinFET silicon, where the structure of transistors are stacked up vertically (in "fins") instead of the flat layout they currently use. TSMC, one of the larger Eastern chip foundries, has just signed a deal with Apple to produce FinFET chips down to a minuscule 10nm scale over the next three years. Married to the Michigan innovation, this innovation could easily mean 2020's smartphones are like pocket supercomputers.
[Image: Flickr user Orin Zebest]