Modern supercomputers are essentially clusters, but with much more advanced network topologies and technologies, shared storage, etc. It's not just one monoloth

Modern supercomputers are essentially clusters, but with much more advanced network topologies and technologies, shared storage, etc. It's not just one monolothic machine. However, the types of computation performed by the top supercomputers are rarely the "embarassingly parallel" programs you can easily distribute via an @Home-style program, or something like Hadoop. They do depend heavily on very reliable, very low latency, high bandwidth networks.