Supercomputers can store more information than the human brain and can calculate a single equation faster, but even the biggest, fastest supercomputers in the world cannot match the overall processing power of the brain. And they are nowhere near as compact or energy efficient.

Nevertheless, IBM is trying to simulate the human brain with its own cutting-edge supercomputer, called Blue Gene. For the simulation, it used 147,456 processors working in parallel with one another. IBM researchers say each processor is roughly equivalent to the one found in a personal computer, with one gigabyte of working memory.

So configured, Blue Gene simulated 4.5 percent of the brain's neurons and the connections among them called synapses—that's about one billion neurons and 10 trillion synapses. In total, the brain has roughly 20 billion neurons and 200 trillion synapses.

IBM describes the work in an intriguing paper (pdf) that compares various animal simulations done by its cognitive computing research group in Almaden, Calif. The group has managed to completely simulate the brain of a mouse (512 processors), rat (2,048) and cat (24,576). To rival the cortex inside your head, IBM predicts it will need to hook up 880,000 processors, which it hopes to achieve by 2019.

Read more about Computers vs. Brains in the November 2011 issue of Scientific American.