 The Portals network programming API is used to ensure inter-processor communication can scale as large as the entire system, and has been used on many different supercomputers, including the Intel Teraflops and Paragon.The compute processors use a custom lightweight kernel operating system named Catamount, which is based on the operating system of ASCI Red called "Cougar".A userspace implementation of the Lustre file system, named liblustre, was ported to the Catamount environment using the libsysio library to provide POSIX-like semantics.