January 27, 2012 issue of Science published a very interesting NEWSFOCUS on "What It’ll Take To Go Exascale". Here is the abstract:
To accurately simulate global climate, researchers will need supercomputers more powerful than any yet designed. These so-called exascale computers would be capable of carrying out 10^18 floating point operations per second, or an exaflops. That’s nearly 100 times more powerful than today’s biggest supercomputer, Japan’s "K Computer," which achieves 11.3 petaflops (1015 flops), and 1000 times faster than the Hopper supercomputer. The United States now appears poised to reach for the exascale, as do China, Japan, Russia, India, and the European Union. Advances in supercomputers have come at a steady pace over the past 20 years, enabled by the continual improvement in computer chip manufacturing. But this evolutionary approach won’t cut it in getting to the exascale. Instead, computer scientists must first figure out ways to make future machines far more energy efficient and tolerant of errors, and find novel ways to program them.