Five dimensions? WTF?

By this point you can probably tell where things are going. At IBM Research in Zurich, they are working on a technology that solves both power delivery and cooling in vertically stacked electronics, with the eventual goal of enabling the creation of skyscraper CPUs, GPUs, or whatever other IC you might fancy.

Somewhat unfortunately, IBM calls this research program "towards five-dimensional scaling." Not three dimensions, like you might expect of a project tasked with stacking 2D chips on top of each other to form 3D piles, or perhaps four dimensions if you had done a module in marketing at university and were feeling exceedingly generous, but five.

Fortunately, however, IBM's five-dimensional scaling tech doesn't require an understanding of string theory. Rather, the fourth and fifth dimensions are rather mundane: number four is power delivery, and cooling is number five.

As the video above clearly shows, IBM Research's work on electronic blood is at a very early stage. It does actually work, though. In the setup that I described at the top of the story, the researchers have managed to use their electrochemical blood to provide about 10 milliwatts of power to a computer chip. In theory, the blood also kept the chip cool—but the device was so low-power that it only produced a negligible amount of heat anyway.

The cooling probably won't be a problem, though. IBM's work on 5D blood stems from its advanced liquid cooling and microfluidics research. IBM, as you're probably aware, is a big player in the supercomputing sector—an arena where improved cooling technologies can result in huge computing power and efficiency benefits.

A few years ago, IBM's research into liquid cooling resulted in the creation of two "hot water cooled" supercomputers: one at ETH in Zurich and SuperMUC at the Leibniz Supercomputing Centre in Germany. More recently, we covered the Solar Sunflower, where instead of using conventional copper water blocks to ferry heat away, water flows through micron-thick microfluidic channels that have been carved out of a silicon wafer. The Solar Sunflower story has more details if you want them, but the general gist of it is this: microfluidic liquid cooling could be really, really useful, both in terms of the absolute amount of thermal power that can be dissipated, and also in relieving those hard-to-reach hot spots.

IBM

IBM

IBM

The power delivery side of the equation is likely to be a bit trickier. Basically, IBM needs to start with its microfluidic cooling tech and then modify the cooling medium so that it also carries soluble redox couples (i.e. a compound that can be oxidised to produce some electricity, and then reduced again to recharge). Then, instead of just providing microfluidic channels on the chip for cooling, there also needs to be a few extra bits to complete its transformation into a redox flow battery.

If IBM can work out how to do all of these things, though, the numbers from one of their research papers sound pretty good. The complete charge-discharge cycle of the electrochemical blood "has energy efficiencies of more than 80 percent," with a voltage of around 1V. That could well be good enough to power a stack of computer chips.

The blood-brain barrier

Why, you might ask, is IBM calling it 5D blood, though? Well, the original inspiration for the research was biological efficiency. That is, despite how small our transistors are getting and how fast our interconnects are becoming, animal brains are several orders of magnitude more efficient in terms of computing efficiency and density. Some of the world's largest supercomputers have a total processing power that approximates a small mammal, but they require about 10,000,000 watts to get there. The human brain, by comparison, uses maybe 20 or 30 watts at full bore. A supercomputer is just slightly larger than a mammalian brain too.

Those gaping gulfs in efficiency and density may begin to be bridged by neuromorphic (brain-like) chips, and other bleeding-edge advances in CMOS logic, but they'll only get us so far. To get towards biological levels of efficiency (and perhaps intelligence as well), we need some way of cramming millions of computer chips into a space the size of a shoe box—or, er, a human skull. Animals use blood for both energy delivery and cooling of the most efficient computers in the world, so why shouldn't IBM?

IBM Journal of Research and Development, 2011. DOI: 10.1147/JRD.2011.2165677 (About DOIs).