Here is an analysis of how various factors including engineering improvements could see a

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Here is an analysis of how various factors including engineering improvements could see a system go from 6 months to 18 hours of execution time. Not a classic case of a failure based post-mortem because there was nothing at stake here but it does give you insight into the details of how many small improvements can give an overall large improvement.

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Lots of deep technical info on that blog. See also the docs for the fractal program:
http://www.cygnus-software.com/docs/html/64bitcalcs.htm