Brute force key checking parallelizes very nicely, so using a cluster
of 16 computers gives basically the same MIPS rate as using the 16
computers separately. It's more interesting to see these machines
work on problems that are NOT so clearly parallelizable.
If you are still interested in building your own cluster, take a look
at PAPERS, a project here at Purdue. To quote the professor behind
it, "You can build the hardware in your kitchen for less than $50 of
TTL chips...in fact, that's how I do it."
-- Mike Gebis gebis@ecn.purdue.edu mgebis@eternal.net