 The systems that supported virtual memory, the Spectra 70/46 and 70/61 and the later RCA 3 and 7, could also run the RCA's Virtual Memory Operating System (VMOS).VMOS was originally named TSOS (Time Sharing Operating System), but was renamed to expand the market for the system beyond time-sharing.TSOS was the first mainframe, demand paged, virtual memory operating system on the market.