Your old 486 has the potential rival the big iron of supercomputers.
You just need the right sort of software or coding skills and a whole bunch of old 486s hooked together via ethernet. The idea is called distributed computing. What you do is divide a supercomputer sized problem up, give each small piece to smaller, stupider computers and combine the calculations at the end, solving the problem with supercomputer speed. The SETI@Home Project and the Mersenne Prime Search work this way. Scientific American, has come out with an article on the subject recently.