The search for the lost Cray supercomputer OS tells the story of someone trying to make a model of the Cray-1. As the premier supercomputer of its day in 1971 it had 1MB of RAM and could perform 80M FLOPS. It also weighed 5.5 tons.
Given that your phone (well my phone and probably yours) is more powerful, two guys decided to make a 1/10 scale model that fit on a desk. The guts are a $225 computer board. The hard part was finding Cray software. It's a fun read.