The Altix was the most powerful computer in the world in 2006, assuming that a "computer" is defined as a collection of hardware running under a single instance of an operating system. The Altix had 512 Itanium processors running under a single instance of Linux. A cluster of 20 machines was then the eighth-fastest supercomputer. All faster supercomputers were clusters, but none have as many FLOPS per machine. However, more recent supercomputers are very large clusters of machines that are individually less capable. SGI acknowledged this and in 2007 moved away from the "massive NUMA" model to clusters.