EOS (operating system)

EOS is a discontinued operating system developed by ETA Systems (a spin-off division of Control Data Corporation) for use in their ETA10 line of supercomputers in the 1980s.
Overview.
EOS was preceded by and was binary executable compatible with the CDC VSOS operating system for Cyber 205. Like VSOS, EOS had demand paged virtual memory (the VS part) with 2 pages sizes for improved virtual memory performance with the ETA's faster hardware pipelines. Though it had roots in the interactive Livermore Time Sharing System (LTSS), VSOS was focused as a batch-oriented operating system. VSOS was not run at very many institutions and its application-oriented performance, while the historic focus for supercomputing, set its features behind the times because of its limited user base.
To address this feature deficiency and to make the operating system more "normal to use", the VSOS characteristics were married with UNIX characteristics in a hybrid OS. The OS was intended to be effective for both batch work that drove the hardware to its maximum or for interactive use in development from a UNIX workstation.
EOS was written mainly in Cybil, a Pascal-like programming language created by Control Data for its later Cyber operating systems. It was a new effort, as VSOS was implemented in IMPL, a Fortran-like language created for the LTSS implementation. The command line appearance of all these systems was similar to the lineage going back to UNIVAC EXEC*8.
EOS was released with early hardware deliveries and had some of the typical problems for early OS releases. Some customers delayed payment for their supercomputer installations.
ETA later released a port of UNIX for the ETA-10 line, which was more quickly accepted by their customer base. However, this port started as a single-processor kernel which did not transparently exploit the hardware architecture with up to 8 large application CPUs for applications.