april 2016 - 

it’s general knowledge that heat is a significant problem with modern microprocessors. intel and amd have collectively held the line at 140w maximum tdp (thermal design power) for the past decade, with a few skus tiptoeing up to 150 or 165. but shrinking die sizes and an end to historic voltage scaling have made it harder and harder to hit high frequency targets. darpa has a new project to cool processors through the use of microfluidic channels that pass directly through a processor and move microscopic amounts of water into direct contact with hot-spot areas.

why do hot spots form?

hot spots are an increasing problem in microprocessor design for two reasons: first, transistor density has continued to increase over the past decade, even as clock speeds have flatlined. this means more and more transistors are packed into a smaller space, which means each transistor has less and less area to dissipate heat. the second problem is that cpu voltage largely stopped scaling. the chart below captures this:

this chart shows cpu voltages and feature sizes graphed in micrometers (0.13 = 130nm, 0.03 = 32nm). 130nm cpus shipped 15 years ago with operating voltages between ~1.5v and 1.75v. jump back 15 years again, to 1985, and intel’s 80386 required 5 volts. in 1994, the 486dx2 used an operating voltage of 3.3v. amd’s k6, in 1999, had an operating voltage of 2.1v. had this scaling continued, modern microprocessors would require well below 0.5v today.

read full article here: http://www.extremetech.com/extreme/224516-microfluidics-darpa-is-betting-embedded-water-droplets-could-cool-next-gen-chips

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