Firstly, in the area of Operating System, Linux (in a number of variants, notably SLES and Red Hat) holds 450 places.  Of the remainder, AIX holds 21 places and Windows HPC 2008 just 4; sorry Bill.

As the introduction suggests, Intel CPUs are becoming dominant.  In fact since 2000, when they first appeared in the list with just a couple of entries, they have become the dominant force – peaking in the current list at 399 systems.  Of the remainder, AMD hold 43 places, meaning that the 'Intel platform,' with 442 places, is almost as dominant at the Linux Operating System.

Of the rest, 51 are PowerPC, leaving just 7 other processor systems.

From Intel's announcement of their success, "Intel-based super computing platforms are playing a pivotal role in a number of research areas, from improving the safety of space exploration to forecasting global climate conditions.  More 'mainstream' industries, such as financial services and health care, are also using Intel-based systems to achieve faster, more accurate results, to speed the pace of innovation and improve competitive advantage."