I'm afraid I have to disagree, -brazil-. Supercomputers are used for exceptionally difficult problems, such as weather prediction and especially nuclear weapons research. The new Blue Mountain system, made by Silicon Graphics and installed in New Mexico, consists of well over 1,000 processors. Its purpose? Nuclear research, and it's currently one of the three fastest systems available for the purpose. Rather than bang away at a problem with a few centralized processors, the problem can be broken into thousands of parts, worked on, then re-assembled. If you wish to make another comparison, look at distributed computing with the SETI system. Thousands of folks are donating spare CPU ticks to search for extraterrestrial life. They break the problem into tiny chunks, send it out to get processed, then the data is reassembled. If a supercomputer could crank through the data faster, they would've used a Cray and finished the job. It's faster to use many processors to do bits of work.

rp says WonkoDSane says (to me, by mistake) I don't want to add a response WU to Beowulf Cluster, but you may want to add that the other reason why SETI doesn't use one big SC is because it can't afford to do such things.