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The Univac 90/70 was a member of Univac’s Series 90 Family of mainframe class computer systems. The low end family members included the 90/25, 90/30 and 90/40 that ran the OS/3 Operating System. The intermediate members of the family were the 90/60 and 90/70, while the 90/80 was the high end system. These systems all ran the Univac’s virtual memory Operating System, VS/9.
The Series 90 systems were the replacement for the 9000 series of low end, mainframe systems marketed by Sperry Univac during the 1960s. These systems were byte machines with an instruction set that was compatible with the IBM System 360. The family included the 9200, 9300 and 9400 systems and the 9480 ran a real memory operating system called OS/4. As Sperry moved into the 1970s, they expanded the 9000 family with the introduction of the 9700 system in 1971. They were also developing a new real memory operating system for the 9700 called OS/7.
However, in September 1971, the RCA Corporation announced that it was abandoning the computer industry and Sperry was able to acquire RCA’s Computer division. RCA had marketed the Spectra 70 Series (70/15, 70/25, 70/35, 70/45, 70/46, 70/55, 70/60, 70/61) that were compatible with IBM’s 360 series and the RCA Series (RCA 2, 3, 6, 7) competing against the IBM 370. These systems all ran RCA’s real memory operating systems, DOS and TDOS. RCA’s Virtual Memory Systems, the Spectra 70/46 and 70/61 and the RCA 3 and 7 could also run their Virtual Memory Operating System, VMOS. VMOS was originally named TSOS (Time Sharing Operating System), but was renamed in order to expand the system beyond the time sharing market. In fact RCA was credited with coining the term Virtual Memory. TSOS was the first mainframe, demand paging, virtual memory operating system on the market. At the time, IBM was in the process of transforming OS/360 to a Virtual system through the OS/MFT and OS/MVT Operating Systems, on the way to the subsequent release of MVS.
So, in January 1972, Sperry officially took over the RCA base. Sperry would ultimately rethink the 9700 and killed OS/7. They redesigned the 9700, added virtual memory and the Processor was named the 90/70. VMOS was modified for the new hardware platform and was named VS/9. The 90/70 was then modified to produce the 90/60, I understand a NOOP instruction was inserted into the micro-code to statisize an instruction along with an additional wire. This produced a slower version of the 90/70 that would be sold at a lower price. In 1974, Sperry would also replace the low end 9000 systems with the low end Series 90 Family; the 90/25, 90/30 and 90/40 that ran the OS/3 operating system, but that's another story.
A surprising number of the RCA customers continued with Sperry and the 90/60 and 90/70 would provide an upgrade path for the customers with 70/45, 70/46, RCA 2 and 3 systems. In 1976, Sperry would add the 90/80 at the top end of the Series 90 Family, that was based on an RCA design, providing an upgrade path for the 70/60, 70/61, RCA 6 and 7 systems. My customer committed to an upgrade to the 90/60 in 1973. Until the 90/60 system could be delivered, their Spectra 70/45 was replaced with a 70/60 which was field upgraded to a 70/61 and their applications were converted to run on VMOS. In 1975, they took delivery of their 90/60 and were able to run their applications directly on VS/9.
The RCA base was very profitable for Sperry and Sperry was able to put together a string of 40 quarters of profit. Sperry was also able to build the 1100 family of systems and the 1100/60 provided an entry level system for the Series 90 customer base. So around 1982-83, Sperry announced they would cap the Series 90 Systems and would decommit the VS/9 operating system to concentrate on the 1100 series. After this announcement, Sperry would stumble on the revenue side ending their run of profitable quarters, resulting in some downsizing. I believe the Series 90 Systems were under pressure from IBM’s 4300 series systems that offered tremendous price performance value and may have been the reason Sperry wanted to concentrate on the 1100. This was also the era of the VAX and within a year or two, DEC would pass Sperry in terms of total revenue to become the number two U.S. Computer manufacturer.