Supercomputer nowadays uses massive parallelism -- TH-2 use more than 3 million cores, for example. for supercomputer, more time and energy is actually used to move the data around rather than in computation. TH-2 uses Intel Xeon E5, which is NOT the fastest Intel CPU. However, it has a large cache -- to minimize data and instruction fetches, and it has lower power/throughput ratio than faster chips.
Power consumption is important -- because more powers need more cooling, and it makes the system less dense, hence more distance between hardware and increase latency. Power is also expensive also -- the power required to run a supercomputer like TH-2 can run a sizable city.
