EWS-UX / V: Based on Unix SVR2. It runs on the EWS4800 series equipped with the MC68020, MC68030, and MC68040 processors.
EWS-UX / V (Rel4.0): Based on Unix SVR4. It runs on the EWS4800 series equipped with R3000 (VR3600 [jp]) and R4000 processors.
EWS-UX / V (Rel4.2): Based on Unix SVR4.2. It supports processors such as the R4400, VR4200 [jp], and R4600.
EWS-UX / V (Rel4.2MP): Based on Unix SVR4.2MP. It supports multi-processor systems using the R4400MC. It is mostly similar to UP-UX, NEC's Unix operating system for servers.
^van der Steen, Aad J; Dongarra, Jack J (May 1996). Overview of Recent Supercomputers(PDF) (Report) (6th ed.). University of Tennessee Knoxville. pp. 35, 67.