How well has Dill’s prediction held up? In 2000, the first ever microsecond-long molecular dynamics simulation of protein folding was reported. It required 750,000 node hours (equal to the product of the number of hours times the number of processors) of computer time on a Cray T3 supercomputer. According to Dill’s prediction, this length of simulation was not to be expected until around 2010. However, as noted above, Dill’s analysis does not take into account large-scale parallelization—which, unless the computation is communications-limited, will effectively increase the speed of a computation in proportion to the number of processors available.

Time scales for various motions within biopolymers (upper) and nonbiological polymers (lower). The year scale at the bottom shows estimates of when each such process might be accessible to brute force molecular simulation on supercomputers, assuming that parallel processing capability on supercomputers increases by about a factor of 1,000 every 10 years (i.e., one order of magnitude more than Moore’s law) and neglecting new approaches or breakthroughs. Reprinted with permission from H.S. Chan and K. A. Dill. Physics Today, 46, 2, 24, (1993).