It was announced in February 1966 and shipped in April, becoming a major part of Tymshare's expansion during the 1960s.
The design was originally created by the University of California, Berkeley as part of their Project Genie that ran between 1964 and 1969.
The 940 was simply a commercialized version of the Genie design and remained backwardly compatible with their earlier models, with the exception of the 12-bit SDS 92.
Like most systems of the era, the machine was built with a bank of core memory as the primary storage, allowing between 16 and 64 kilowords.
The SDS machines also included a paper tape punch and reader, line printer, and a real-time clock.