[marci]

It's not necessary about speed, it's about how to write code that runs efficiently, concurrently and/or in parallel on that many nodes.

IIRC, that's kinda how ethernet came to be, ther were working on the computing world of the future at xerox PARK, they had to create clusters to emulate the cpu power that would be available in the coming years. Looking at the current trend, from phones to servers, they go from two cores to I-don't-have-enough-fingers-except-if-I-count-in-binary cores. A 3000 cores raspberypi cluster can be an emulation of the computing environemnt of tomorrow, not in term of raw power, but in term of distributed computing, and lead to unforseen invention as the ubiquitous ethernet.