"In the world of high-end enterprise systems, that top spot--the world of large symmetrical processing UNIX systems--is divided between the tier 1 systems vendors--IBM, Sun and HP. All of these have their own proprietary architectures--IBM has POWER with AIX, Sun has SPARC and Niagra with Solaris, and HP has the Itanium and HPUX. Only two of these vendors, IBM and HP, are able to run enterprise-supported versions of Linux in addition to their proprietary Unixes on their native platforms, although Sun has experimented in the recent past with Ubuntu on their Niagra chip, a relationship which seems to be waning..."
